The sinister music and jungle scene immediately tells us we're in for a Hood-heavy episode. Sure enough, we see the 'master' criminal sitting next to a roaring fire as he plots against International Rescue. He mutters, "Now your members seek further glory…hunting ancient treasures." But he is determined that this time, "They will fail!" and he flicks a switch that uncovers the statue of his hapless half-brother, Kyrano. The Hood wants the treasure badly and is determined to leave IR "beneath Lake Anasta," and uses his spooky eye-glowing powers to command Kyrano.

In Tracy Island's kitchen, Kyrano cries out and collapses to the floor. I guess he left 'brother of arch-enemy' off his resume. The Hood harries him to tell him when the expedition to Lake Anasta will take place, ordering Kyrano to "speak!" Kyrano eventually gives up that they are leaving the next day to make a survey of the Temple. Who will this affect? And how often has the Hood been checking in with his half-brother about this? What if they'd already been and gone?

After this sinister instruction we immediately have a close-up on Tin-Tin's smiling face as friendly laughter surrounds her. We see she's sitting next to Brains on the couch beneath the Tracy brothers' portraits, and that John (in a natty red waistcoat and ugly green shirt), Scott and Jeff are laughing with them. Tin-Tin has her Air Terrainean flight bag on the coffee table, and both she and Brains seem dressed for casual desert travel. They're joking about the treasure hunt ahead, with Scott requesting her to save him "a gem or two" as "everybody's giving them as Christmas presents this year". Tin-Tin suggests a "bright little diamond" for John, but he quips that he'd be happier with "a dirty old bar o'gold". Fair enough.

Jeff wonders just how convinced Brains is that they'll actually find "buried treasure," but Brains is "90% certain" that something is under the lake. Scott butts in here, pointing out that it's as great an excuse "as any" to "have a vacation," and seems extremely interested in the "fetching new swimsuits" that Tin-Tin had had sent out to the Island. With all this gentle flirting going on, Alan is conspicuous by his absence here, especially if Tin-Tin and Brains are off for a few days, and even if he probably is in Thunderbird Five right now.

Jeff says that Brains and Tin-Tin deserve the break, and greets Kyrano, who appears to have finished the packing for the pair. He also doesn't seem to have told the family about his little collapse the day before, as nobody asks him if he's feeling better this time. Then Virgil's portrait lights start to flash, which is a sign that he's ready for takeoff. Jeff sends Brains and Tin-Tin to Thunderbird Two's passenger chute and tells them that he and Kyrano will wave them off from the runway. Scott is on 'talkback' radio duty. Seconds later, Thunderbird Two is away.

In keeping with the "vacation" spirit, Virgil is in his civilian clothes as he flies Tin-Tin and Brains to Lake Anasta. Using Thunderbird Two seems like a big waste for this sort of trip, but we'll soon see why they need her. Jeff and Kyrano watch them go from the runway, and Jeff reassures his friend that Tin-Tin will be back in just ten days. However, for some reason, Kyrano has a bad feeling about the trip. Jeff tries to reassure his friend, but just manages to perform his usual 'jinx of Jeff Tracy' magic by saying, "a beautiful lake, miles and miles from anywhere. What could be safer?" If puppets could smack their own foreheads, I'm pretty sure that's what Kyrano would do right now.

After all, the truck we see next, heading across the desert sands, is being driven by the Hood! The Big Bad is already cursing the endlessness of the sand, not unlike the explorers in "The Uninvited!" More "Uninvited" style music plays as the Hood reaches, and we finally see, the beautiful oasis of Lake Anasta.

Thunderbird Two is heading there, too. Tin-Tin is peering out of the cockpit window and spots the pyramids below, which she tries to get Brains interested in. He ignores her. She notes that they're almost at the rendezvous and quizzes Brains on what he thinks "Professor Blakely will be like". Brains tells her that the guy is "quite a character" and "the best man in his field". Perhaps the guy has a tomb-raiding degree?

Just before they reach the rendezvous, Virgil reminds them of some ground rules. When he drops them off he says they've "gotta move fast" as they can't let the Professor know they're connected with International Rescue "in any way". Well, duh. Tin-Tin assures him that they'll tell Blakely (if he asks) that they "came out to the Middle East by charter flight". Good cover, guys, handy for us to know, too. Next, Virgil asks Brains if he's all set, and after Brains' "FAB" he sets the intrepid pair down in the Pod, and they drive out in their truck, plus several caravans! Brains drives the truck and Tin-Tin is navigating. They have 'Anasta Expedition' written on a sticker on the front of their truck, maybe in case someone turns up in the same truck and makes off with theirs? Now Virgil radios Scott to let him know that he's on his way home again, and Scott tells him to "keep in touch". Thunderbird Two leaves.

In the expedition truck, Brains hopes that their "sort of secret landing passed off sort of secretly", heh. They'll be meeting up with the mysterious Professor Blakely at some crossroads, as he's coming from the only other desert highway. Music not unlike that usually heard in a Laurel & Hardy film plays as we see a rickety cab, 'Hassan Ali, Luxury Taxis, Distance No Object'. It's definitely not air-conditioned, either. The passenger, presumably Professor Blakely, is justifiably concerned by the explosions coming from the ancient car – although he hasn't seen the huge tariff he's totting up on the screen behind him. Maybe Jeff is footing all the expenses for this trip? His dodgy Arab taxi driver (ah, harmless 1960s racism ahoy!) assures Blakely that he is an "exquisite driver" and that they've just got half a mile left to go.

At the rendezvous point, Brains and Tin-Tin luxuriate in the airconditioned caravan-come-cocktail bar while they wait for the Professor. Brains comments how much they need the air-con, considering it's "up to 112 in the shade outside". Then they hear two loud bangs and horn honking. Brains exclaims, "Professor Blakely, I presume?" That sounds awfully familiar, Brains, old chap. Somewhat improbably, the good Professor has made it across the desert in a bucket of bolts to reach them. I have my doubts that the driver will make it back, mind you.

Blakely greets Brains with full bluster, rather overdoing the "What, what, what?" and "old boy," and blowing off Brains' introduction to Tin-Tin with a brusque, "delighted, I'm sure, charming, charming". After he baffles Brains more by saying, "The proof of the pudding is in the eating and all that, what what what?" Brains brightly asks him what he'd like to do first.

The Professor recommends a recce of the lake, and heads over to pay the cab driver. The fare is five shekels – is that cheap..? The chap seems pleased and wishes the Professor "good safari". I note the ragged pictures of a leggy girl and a old sports car glued to the dodgy driver's back window. Nice detailing here. The cab heads off into the desert, and almost certain death, with another couple of explosions and a jaunty honk.

Brains offers Blakely a "cooling drink" in the cocktail caravan before they set off for the lake. Blakely agrees that the treasure can wait a little longer, as he doubts that "anyone's gonna steal it from under our noses…" Well, actually…

The Hood's truck backs up to the lake shore and deposits a small blue submarine (nicked from some Soviet state?) into the waters. More spooky music plays. I have to wonder where he'll stash his truck.

The International Rescue treasure hunters get closer to the Lake. Tin-Tin points out the Anasta pipeline, which means they're very near. They get excited as they reach the lake, but fail to notice the Hood's periscope poking out as he spies on their arrival. From the sub, he gloats that his "friends" are "dead on time". Gulp.

On the shore, Brains and Tin-Tin have already suited-up ready for their dive. Tin-Tin reflects that they'll be the first ones to see the temple in over one hundred years. The Professor warns them that in that time the stonework may have become "treacherous" and to "be careful". Brains assures him that they will.

Once they head underwater the Stingray flashbacks come thick and fast, including the dreamy score that accompanies these diving scenes. There's remarkably good visibility as they reach the temple, and Brains repeats Blakely's warning to Tin-Tin as he says it really "doesn't look too solid". The Hood is spying on them from the sub as they swim on, and he gloats that they will lead him "straight to the treasure". As Brains and Tin-Tin swim through the pretty ruins, he ponders which column could contain the treasure? Tin-Tin suggests one, perhaps at random as there seem to be loads. However, Brains thinks she may be right, and when they reach it he says it could be "the one". Maybe the Hood isn't the only psychic in the family?

Tin-Tin suggests taking "a sample" of the pillar to the Professor. Brains uses a small pickaxe to prise out a layer of rock from the "central column", which the Professor – on the radio – says he is eager to take a look at "before lights out". Creepy warning music plays as Brains carries back the lump of temple column, with Tin-Tin close behind him.

The Hood immediately leaps to the conclusion that the pair have found something. Let's take a moment to absorb his patented grey boiler suit and black corset detailing along the chest, available from any Evil Genius clothing department. As we're doing that, the Hood leaps a little further, assuming that "They have found the treasure!" and plotting to "persuade them to tell me" where the rest is. Eeep.

In the caravan, Brains is extracting a dirt-covered coin from the column sample. He hands it to the Professor, who says he's "glad" to say that the Anasta Expedition "is a success" and that "you have located the lost treasure". Awesome. Now what do they all do for the next nine days? Tin-Tin is thrilled and says they "must radio Mr Tracy right away and tell him."

Night falls over the camp, although it's lit up by a full moon. Brains is still examining the "beautiful" artefact they've found and said he "always knew" his theory was correct – I'd like to know more – and he's looking forward to their work tomorrow when they can collect "lots more evidence". I still wonder how he knew where to look. Just then, there's a tap at the door. Brains seems puzzled and opens it – the Hood is right there, disguised as an Arab nomad. Brains is startled and demands, "Who are you? Whaddya want?" but the Hood quickly zaps him with his glowing eyes (apparently they're good for more than just getting aroused by the thought of gold). Brains collapses, losing his glasses on the way down. The Hood removes his mask. Maybe it's a bit hot being underneath it. Anyway, things look bad for the little expedition.

It's daytime on Tracy Island and Kyrano's innocently working in the kitchen when Scott wanders in with "great news" about Brains' call the night before, telling them that they'd traced "the lost treasure". I guess Jeff wasn't dying to find out, then? Or he'd left Scott by the phone for the evening. Jeff rumbles that "that is good news" and Scott tells them the rest of what Tin-Tin and Brains had been up to – which we already know. Jeff says he'll "convey them our congratulations" on the next routine call, then he notices that Grandma looks like she "swallowed her egg spoon," and inquires what wrong. Well, she does look like that. Grandma wonders grumpily why Tin-Tin needs to go treasure hunting when she has "enough pretty jewellery already". Her voice reminds me of a kinder Mrs Norman Bates. Scott gently assures his grandma that Tin-Tin and Brains aren't going to "rob the temple" but that they're doing it for "science" and says that whatever they find will go back with Blakely "to the International Museum of Archaeology". So that's OK then. Jeff sends everyone off to work and says he's going to wait upstairs for Brains' next call. He muses that the Anasta team "must be feeling pleased with themselves".

Naturally, Jeff's lines are given huge ironic status given the current state of the little team. We see that Brains is buried up to his neck in the sand near the lakeside, deeply dazed and confused. He mumbles, "What happened?" and can remember only a stranger and his "staring eyes". As he calls for help, his voice sounds awfully thin and distant as it carries over to the far off caravans. He shouts for Tin-Tin and the Professor, but inside her caravan, we see she is sitting motionless in a chair by her dressing table, staring at nothing. Blakely must have put up more of a fight, and he seems to have had the stuffing knocked out of him, currently lying unconscious amongst the broken mess on the floor.

Brains is now terribly thirsty and wishes he could get to the radio. Just then the Hood cackles above him, asking, "What would you do then, my friend? Inform your friends at International Rescue?" He sneers that this is "out of the question". The Hood has changed all the way back into his disguise as a nomad tribesman, looking very intimidating above poor Brains' exposed head. To his credit, Brains first demands to know what the Hood's done with the other two, but instead the Hood grills him on the location of the treasure. Then Brains just pleads for water. The Hood demands again to know where the rest of the treasure is. Brains keeps begging for water. The Hood promises that if Brains tells him where the gold is "I shall let you and your friends go". Riiiight, sure you will. Brains passes out.

Back on Tracy Island, Jeff "doesn't get it," as Brains has "never been late before," and there's been no radio contact of any kind with the expedition at the Lake. He sends a worried looking Kyrano off to get Scott. As Jeff tries to call Lake Anasta again, we see that Tin-Tin remains hypnotised and unresponsive next to the radio at the other end. There's no automatic radio signal, either, and Jeff seems more concerned than ever.

Scott arrives, asking, "What's up, Father?" He adds that Kyrano seems to think there's "something wrong at the Lake". Jeff still isn't sure and tells Scott that Brains is fourteen minutes overdue to check in, then asks his son how Brains sounded when he spoke to him the night before. Scott says they seemed to be in good spirits and were about to go to bed. He supposes it could be "they're just busy". Jeff doesn't think so, and Scott agrees that it's "not like Brains to lose contact completely, like this…" and just then an urgent beeping noise goes off over the radio. It's the emergency beacon!

At this, Jeff sends Scott out right away and tells him that Virgil will be coming right after him. We can still only speculate on how Brains managed to set off an emergency beacon considering his position.

At the camp of doom, Tin-Tin is still frozen and Brains remains buried up to his neck out in the hot sun, muttering desperately for help and water. Cruelly, he's in full view of the lake. The Hood spies on him, having for some reason nipped back to his submarine. He decides he will grill Brains again in a very precise "nine minutes" time to see if he's changed his mind. He gloats that "no man can stay in the burning sun for long without having his tongue loosened". Although I'm sure heat stroke might make interrogation somewhat unpredictable. However, the Hood's plans are about to be scuppered as Scott flies in to check out the area.

Scott tells Jeff over the radio that the camp is quiet, "Maybe too quiet," and that he can't see any sign of Brains or Tin-Tin. A worried Jeff orders tri-circuit contact at all times between base and T-Birds 1 and 2. Just as Virgil confirms that he's three minutes away, Scott yells out that he can see Brains "Down below in the sand…buried…up to his neck!" and announces that he's landing now. Grandma shouts back to ask about Tin- Tin, but Scott doesn't respond. Instead, we get the Hood's point of view from the lake, as Scott lands nearby – but hopefully not on top of – Brains.

The Hood is perturbed that they have found his "victim in the sand" but plots to turn this setback into a plan to "destroy International Rescue utterly". He's only going to destroy them "after they have led me to the treasure" though. It seems that bad guys just can't pay the rent with a few photos of Thunderbirds craft anymore. Maybe he's trying to increase their scarcity?

Thunderbird Two arrives overhead with an ETA of one minute to go. Meanwhile, Brains begs for water as Scott reaches his side and kneels down to speak to him. Brains is pleased to see him, adding, "Where's Tin-Tin?" Scott doesn't know, but he looks extremely worried and assures Brains that they'll "soon find her." And he tells Brains not to worry, "I'm gonna get you out of there." Brains looks suitably dehydrated and his chapped lips are painful looking. The Hood gloats and starts to photograph the IR machines as Thunderbird Two lands. The Automatic Camera Detector starts to beep in One's cockpit, but Scott isn't there to hear it – he needs a remote on his wrist or something!

Virgil opens the caravan door with a frowny face, and exclaims, "Tin-Tin!" as he sees her staring motionless. Scott and Gordon are tending to Brains after pulling him out of the hole, and Scott dabs the poor guy's head with a cloth. Aww. Scott asks how Brains feel now and Brains says he's all right, but worried about Tin-Tin. Gordon assures him that she's OK, but "the Professor's not so good". Virgil questions Tin-Tin on her bed, and there's lots and lots here for Tin-Tin/Virgil fanfic writers to get excited about, as they are looking very cosy together and she has one hand on his thigh as she holds his other hand. She's dazedly telling him about a stranger with "terrible eyes" that she couldn't look away from, and that she was "slipping away all the time". Virgil asks if she might recognise the guy but she says she'd never seen him before. She does, however, hint that she "felt" she knew him "in some far off way," and then tells Virgil that she's still very sleepy. He warmly tells her to "take it easy" and that Scott is letting base know they're OK.

Jeff tells Scott that they're "all mighty relieved" at the news, and wants everyone from IR to return in the morning, once Professor Blakely's been helicoptered (not helijetted?) away. Scott enquires about the status of the expedition, and Jeff tells him sternly that IR wasn't set up for "treasure trails" and Brains' hunt will have to wait for now.

Back in the cocktail caravan, Brains seems to be feeling better, sitting with Tin-Tin, Virgil and Gordon. He's worried about the Professor, but Gordon repeats that Blakely is OK, although still unconscious. Scott returns to ask how the "invalids" are, clearly happy that they're both all right. He tells them that Jeff is arranging for the helicopter to "ship out" Blakely to hospital in the morning and that then they all have to "hot foot it" back to base. Brains muses that Jeff's right and that they "do seem to have caused a lot of trouble". His lips are still very chapped, the poor thing.

Scott adds that he just noticed, after talking to Jeff, that the Automatic Camera Detector had been operating. He doesn't seem REALLY concerned, though. Gordon can't believe anyone is taking photos of "Thunderbird in this area". Two things – first, surely they realize it was probably whoever attacked the camp? Do they even have anyone on watch? Second, why do the characters, every so often, call the machines plain old 'Thunderbird'? It just feels like an odd way to refer to the individual machines.

Brains has at least figured out that they've wandered into a full-scale trap, although he gives the Hood too much credit when he thinks that the "whole operation" was used by their "enemies" to draw them to a "lonely spot", and the trap. Unless the Hood laid the groundwork for Brains' interest in the treasure, and that doesn't seem likely, then Brains really doesn't know that the criminal's just been lurching from one half-assed plan to the next for as long as we've known him! And speaking of the Hood, we see that he's still lurking near the underwater temple in his little blue submarine.

Night time again, and Tin-Tin is fast asleep in her bed when the door opens. Is it Virgil? Is it – the Hood! Nope. It's Brains, saying "sssh" and still badly in need of some lip-salve. Tin-Tin demands to know what he's doing up at "this time of night?" and he says he hasn't been able to sleep out of guilt, following what Mr Tracy said about all the trouble he's caused, "and to cap it all, we've got someone spying on us." Tin-Tin tries to point out that Jeff probably didn't think they'd done it on purpose, but Brains is already in his wetsuit with the plan to make amends by going into the lake, and finally Tin-Tin at least makes the connection between the spying photographer and the man who attacked them. Brains has also figured out that the spy is probably in the lake itself, which makes his plan to "make amends" all the more baffling.

Brains asks Tin-Tin to keep in touch with him on the radio while he investigates the temple again, and although she doesn't like it, she agrees. We see Brains swim out and approach the temple, where he tugs at more of the column they found earlier, to reveal lots and lots of sparkling jewels! Tin-Tin is more concerned if he can see anyone else down there. Brains says that it doesn't appear so, but he then lifts a rock revealing a thick black wire underneath. This is actually an alarm that alerts the Hood to his presence!

Brains thinks he's onto something and follows the cable, and Tin-Tin just wants to wake up Scott and the others. Brains is sure there's "no need for that, yet", unaware that the Hood is on his way to investigate. It's not very long before Brains swims up to the Hood's intimidating form standing over the wire. The Hood's hypnotic powers don't seem to be diluted by the lake water, and Brains passes out and sinks like a rock. The Hood swims off.

It's dawn, and Tin-Tin has woken all the others, telling them what happened in her bedroom. Scott, Virgil and Gordon have clearly had time to get dressed but not to shave. Virgil is anxious to go and help Brains "right away". The Hood is also anxious, to get the treasure "before his friends find him," and he does this by blowing up the temple. As you do. Huge stones and pillars collapse over Brains' unconscious form.

Determined music plays next as Thunderbird Two lifts up to reveal Pod 4, and a very grubby Thunderbird Four scoots out. Scott looks hot and bothered as he sits on Mobile Control with Tin-Tin perched behind him on the caravan steps. The little yellow submarine zooms underwater to the Temple, and Gordon tells Scott that the building is "in ruins" and doubts that Brains has made it. Well, at least he won't have to share voices with the scientist anymore. Scott tells Gordon to keep looking, as, if Brains is alive, "he's only got about seven minutes of oxygen left".

On the next time check, Scott tells Gordon he has five and a half minutes to go, but then we see that the Hood's sub is sneaking up behind Gordon. Just then Gordon spots some air bubbles behind a felled pillar and tells Scott to hurry down with the "aerostatic lifting kit". He then tells Virgil that he'll start clearing the area. As he prepares, the Hood cheerfully gets ready "to destroy International Rescue, and then collect the treasure". He fires a missile right at Thunderbird Four!

Luckily, the Hood is a lousy shot, and it explodes some distance from TB4. Gordon yells that he's being attacked and to "keep Scott clear" until he calls for him. We see Virgil sitting at Mobile Control, also looking overheated, while Tin-Tin hovers very close to his side.

Underwater there's a major submarine battle going on, although Gordon soon has the Hood on the run. It's Stingray time again, especially considering Gordon's alleged history with WASP. Before long Gordon scores a direct hit and the Hood sees that his craft is flooding. As the blue sub sinks, Gordon says a thoughtful, "Hey…" and the Hood escapes just before his craft explodes into little pieces. Gordon doesn't go after him, though.

The Hood's explosion reaches the surface of the lake, and Virgil demands that Gordon tell him what happened. Gordon assures Virgil that he's OK, and will fill them in later as he's now going after Brains. Scott swims over to him in a natty yellow wetsuit. He got there fast, unless the temple really isn't that far down… He's brought a box marked 'Hydrostatic Hoist".

Virgil tells Tin-Tin to go and make the Professor "comfortable" as the helicopter will be there in four minutes. Then he asks Gordon how it's going. Gordon says that they're "swimming" in Brains' treasure, and that they're about to "release the uplifting kit," which is basically a big white balloon on a pulley. It starts to lift the pillar that Brains is stuck beneath, and of course the rope they use immediately begins to fray badly! There appears to be no earthly reason why this would happen within two minutes of using it, but clearly this rope was made by the same subcontractor who supplied International Rescue with Thunderbird Two's grabs! Scott watches the lifting device anxiously while Gordon hauls Brains clear, then the rope breaks and the pillar hits the lake bed once more with a resounding THUMP. It seems like Brains made it.

The medical helijet – not a helicopter, as they kept calling it – takes off and Tin-Tin watches it go with Virgil beside her. She hopes that Blakely doesn't mind being shipped off like this, "just so he doesn't see that Brains and I belong to International Rescue". Virgil assuages her worries by pointing out that the best thing for Blakely "in his condition is hospitalisation," and he adds that the Professor "sure will get a surprise when he comes to". Oh yes. Treasure!

The screen fades in and out, and in the next scene we see a futuristic hospital. We know this because the ambulance parked nearby looks curvy and a bit space-rockety. In the hospital, Blakely is sitting up in bed and looking in good spirits, saying how "jolly nice" it is of Brains and Tin-Tin to "look him up" like this. Brains says they're glad he's feeling better and Tin-Tin asks how it feels to be a "celebrity", now that the world's heard about the Anasta discovery.

Blakely replies that it's "Pretty fair, m'dear, pretty fair," and he asks what they're both doing over the next few months. Brains tells him that they have a "few commitments" (what could they be?) but asks what Blakely is proposing. The Professor brandishes a big picture of a galleon and tells them that there's another sunken treasure in the Caribbean! Before he finishes saying he thought they'd be interested, Brains and Tin-Tin are making tracks out the door. Tin-Tin lamely excuses them by saying that visiting hours are over, and Brains adds, "Must dash, so long, Professor!" and then the door closes behind them.

The Professor mutters that they're an "odd pair" and assumes that the "excitement" was all "too much for them I suppose, not used to it". I'm curious what he thinks really happened out there.

In the safety of the corridor, Tin-Tin tells Brains that they now need a "nice, quiet rescue to soothe our nerves," and they decide to head back to base. As they go, we see the irrepressible Professor is already poring over a book called, "Treasure the Easy Way". I think IR will be receiving another call for help all too soon!

One of the most complete-feeling episodes of the show's run; the pace of "Desperate Intruder" zips along with plenty of menace and intrigue to keep things exciting. The Hood gets to be properly evil again, even if his little scheme was about as well planned out as usual. The fact that he puts treasure hunting above getting IR's machines is still a little weird, though. The writers still seemed afraid to put the Tracys themselves in any danger, which meant that they didn't do much more in this episode than mop up, after the Hood and Brains both do stupid things. After all, how far did the Hood think he would get once he'd blown up Gordon in the lake? All the same, he gets away once more, and no one seems too worried about what happened to the mysterious photographer.

Putting those criticisms aside, this is also a beautiful looking episode and the imagery – especially Brains trapped in the sand – is extremely memorable. Add in the unanswered questions about the characters, Virgil and Tin-Tin in particular, and there's a great deal to enjoy. It's like a better thought-out version of the Uninvited, with a very similar feel, and I think that Desperate Intruder really achieves a much more satisfying resolution.