"You're sure the main shaft can't be cleared?"

It's not like Scott to question Virgil's judgement. Even now there's no real doubt in his voice. He's asking more out of concern than uncertainty. I share the emotion, restless futility driving me to pace Thunderbird Five's deck as I try to figure out my brothers' next move. With the lift shaft blocked by earthquake debris, extracting the trapped men from the salt mine below is going to be a whole lot harder. Virgil's grim expression says that he knows that too.

"Jammed solid. Even if I tried, this place is too unstable for heavy machinery – "

Five's sensors chime, and one stride takes me to the console, my finger stabbing at the microphone switch.

"Aftershock!"

A blur of movement on the wrist-com screens. The worst of it passes quickly, but the clatter of falling debris continues for long seconds before the first link clears to reveal Virgil's dirt-grimed face. He looks unhurt, his free hand raised to cover his mouth as he coughs the dust from his throat. A mile from the mine, where the evacuated personnel have gathered on the closest stable ground, Scott has weathered the shock too. His sharp blue eyes study Virgil's image and the small cluster of mine foremen behind him, before flicking towards the link to Five and offering me a small smile.

"Thanks, Alan."

"It's what I'm here for."

Not entirely, of course. I've got another role too. I scroll again through the information Five has on the Amarna Salt Mine, hesitating over the plan and rotating it through three dimensions.

"Thunderbird Five to Mobile Control. Scott, there's a fair-sized ventilation shaft driven down from the second level. Maybe...?"

My suggestion trails off, uncertain of its heading. Sure, Virgil could abseil down the shaft, but that's not going to be much help in getting all twelve miners, two of them seriously injured, back up. Thunderbird Five sounds another quiet alert. Another aftershock, this time second magnitude, with a dozen smaller tremors following in its wake. We must be due for a big one soon. Time's running out.

"Virgil!" Scott barks out the name, and I tense instinctively. I know that note in my brother's voice. "The lift-cage. Was it at the top of the main shaft or the bottom?"

"Top." Virgil knows that tone too. Scott's got a plan... and he doesn't like it one little bit. "Looks pretty intact." He glances off to one side, examining it with a critical eye. "Even if we can get it there, I don't know if it'll fit down that shaft of Alan's."

"It will." Scott's fingers are flying across Mobile Control, and I give up on checking the dimensions, knowing he's got there before me. "Just. Gonna be tight." Scott's frown deepens. "You're going to have to rig up a cable from Thunderbird Two. Run it down through the upper level to the top of Alan's shaft, and we'll lower the cage."

"Won't it jam?" I get there with the question before Virg can. Even over the video link I can see the scepticism in Virgil's expression. Trying to winch a tight-fitting lift on a twisted cable, threaded down ramps and along corridors...?

Scott takes a deep breath. "Not if I run a second cable from Thunderbird One to balance out the horizontal tension. We can lower it straight down between us."

"But Scott...!" My protest is immediate. Virgil doesn't bother to voice his own. Scott knows as well as we do how close he'd have to bring One to pull that off, and how unstable the ground is after the first quake. Half the galleries of the mine's top level have lost their supports, and it was fifty-fifty that Two would go straight through them when Virgil landed. Adding Thunderbird One's weight ....

Five sounds another warning. "Aftershock. A big one! Brace!"

Magnitude four point six, and this time, when the dust settles, there're new depressions visible across the salt pan. More and more of the abandoned mines are giving out. I read Thunderbird Five's analysis with dismay. "Sixty-forty on a magnitude six 'shock in the next hour."

"No choice then. Gotta go in." Scott's voice is tight with frustration, aware of the risk but undaunted. "Keep an eye on it, Alan. Give the word."

"F.A.B."

The response spills from my lips with practised ease. The promise it carries is just as automatic.

Thunderbird Five's sensors are already deployed to their fullest. Radar beams sweep the ground second by second, categorising each tremor, watching for the first hint of disaster to come. I monitor them, setting up some of John's familiar algorithms and an innovation or two of my own, as Thunderbird One powers up, lifts and, moments later, settles a few hundred metres from her larger sister. I know Scott will be frowning with nervous concentration, and he's not the only one. I can hear Virgil's distracted tone as he tells the foremen to clear the mine and even here – twenty-three thousand miles from the disaster zone – I watch with my heart in my throat.

Bad enough that Thunderbird Two had to land on unstable ground, without putting Thunderbird One in the same precarious situation. If the choice is between taking that risk and failure though, it's no choice at all. Thunderbird One's winch is needed alongside Two's, so that's where she'll be. Virgil needs another pair of hands in the salt mine so Scott will join him, with caution but without hesitation.

I hear Scott leave the craft and soon the two open communications links merge into a single thread. A brisk inspection of the main shaft and Scott concurs, dismissing the earthquake-damaged route out of hand. Both my brothers have allowed the video link to drop, but their echoing voices let me trace their progress as Scott follows Virgil to the secondary shaft, hauling a hover-bike of gear, and the remote control for One's winch, behind him. Getting the trapped miners out before an aftershock brings their cavern crashing down on them won't be easy, even with two sets of winches to deploy. If it wasn't for Scott's brainwave I'd say there wasn't a hope. With it, with two Thunderbirds supporting the lift cage from the ruined main shaft between them, there might be.

It's up to me to give my brothers that chance. They're trusting me to give them time, to pull them out only when I must – not a moment too soon, and never, ever, a moment too late. It's a burden Scott takes on his own shoulders, whenever he can. He only lets John or me take over when there's no choice, but we've been in action long enough now that this isn't my first rodeo. I listen to the rescue, but my eyes are fixed on the monitors, watching the seismograph's fateful dance. Thunderbird Five is running a thousand simulations a second, calculating the odds, reporting them but leaving the decision in my hands. Only I can make this call.

I let a third magnitude aftershock go by with no more than a sharp order to "brace!" and a brief pause in the rescue. Another. A third, all but lost amidst a thousand smaller tremors that lend a constant rumbling background to my brothers' voices. They're making progress, all but three of the miners are secured in the lift now, but it's taking too much time. We can't have long now, and I'm on my feet in front of the console. My eyes flick constantly from readout to readout, my brow drawn into a tight frown. The lift cage is scraping its way up the makeshift shaft, its metal walls screaming in protest. The rescuees are almost secure, Scott and Virgil with them, but I've got to leave time for them to get clear and into the air, and I know I'm cutting it close, even as I try to predict the unpredictable.

The pattern clears. The probability grid converges. Intuitively, I know that this is it, the last moment, the time to keep the promise I made.

"Scott! Virgil! Get out of there! Now!"

I hear a grunt of effort which stretches out for long seconds before the "F.A.B." of acknowledgement. The scramble that follows is lost amidst the chaotic rumble of sound spilling through the open communications links. I know better than to think they'd leave any of the men behind at this stage. I thought I'd allowed time for my brothers' predictable effort to pull off their miracle, for them to hesitate just a moment longer than logic or self-preservation dictate. Did I allow enough?

This time there're no algorithms to distract me, nothing to do but pace the deck and watch my screens. I call out updates through the comms, reporting the shockwave as it crosses the deceptively flat plain, and the collapse that follows in its wake. I doubt anyone is hearing me. Hollowed by the action of water over aeons, and by the hands of men in a few short years, the salt pan is riddled with caverns and instabilities. The general collapse is natural, just gravity trying to restore balance and close up a vacuum that should never have existed. It feels far from that. It feels like a vindictive hand, reaching out to reclaim the miners it almost seized in the first quake, and my brothers along with them.

Engine warm up on Thunderbird Two. And... come on... come on, Scott... on Thunderbird One. But the shock wave is passing beneath them. Magnitude six point five, more than enough to collapse the ruined mine. Communications cut out, the air too full of static electricity, dust and turbulence for short wave radio to penetrate. I should have expected it. John would have, but it's still a shock to me. In the sudden silence, I realise I'm breathing heavily, my brow damp with perspiration.

For long seconds I can only wait. Displaced air has blasted the billowing dust clouds a kilometre high. They block the optical scanners as effectively as the radio. There is nothing for me to do but think over my actions and wonder if the promise I made was too rash, my decision too slow, and my brothers' trust misplaced. I told them I'd give the word – give them time enough to escape and no more. Had I failed?

Thunderbird Five chimes, and instantly my gaze tracks the alert to its source. The bulk of Thunderbird Two, powering herself through the dust-laden air, is unmistakeable, and the tightness in my chest flutters but doesn't ease. Any second now the radio signal will clear and Virgil will ask...

"Thunderbird Two to Thunderbird Five. This is Thunderbird Two calling Thunderbird Five. Alan, do you see Scott?"

I open my mouth, not sure how to respond, and close it again. Another chime, another alert from my space-borne Thunderbird, a sharp look and I draw in my first deep breath for an eternity.

"Got him on scanners, Virgil. Just behind you."

"F.A.B." Virgil grunts an acknowledgement, and a moment later Scott's voice joins his, the two comparing notes on their close escape. Neither notices when I mute my end of the link and drop back into my chair with a firm nod of satisfaction and a shudder of naked relief.

Promise kept.

The End.