Author's Note: This story contains a bit of a spoiler for Secrets and Lies and comes before Acid Test. It was written for the 2015 Tracy Island Writers Forum "Promise" Challenge, hence the sparklingly original title. ;-)

"This is Assembly Control calling all Zero-X units. Assembly Phase One – Go!"

The Launch Controller checked the weather report again, although he didn't really need to; it was a beautiful day at Glenn Field. Hardly a cloud in the sky, temperature at 92 degrees farenheit, visibility at ten miles. Wind out of the southwest at nine miles per hour. He glanced briefly across at the gnat-like cloud of helijets hovering at the perimeter of the airbase, waiting to capture history in the making. Not his problem, fortunately; the Air Force and Space Agency publicity teams were in charge of the press. The Controller only cared that they stayed out of the fly zone, where they could do no harm to this historic occasion.

He turned his attention to the vast concrete building in front of him, where the show had already begun in response to his command. The closest end, a steep-sided trapezoidal slab emblazoned with ZERO-X in bold red letters, was lowering smoothly into its prepared slot in the ground. From his panoramic perch on top of the control tower, behind the slanted, double panes of float glass that maximized visibility, the Controller couldn't hear the low rumble of the machinery. But his mind supplied the sound anyway, because he'd been out there on the tarmac so many times during the testing phase. This launch was the culmination of five long years of building and preparation, and he had been there every step of the way.

As the entrance leveled off, the hangar building itself began to move backwards on its embedded tracks, gradually revealing the sleek steel-blue body of the craft within. Veteran though he was, the Controller still felt his pulse quicken with excitement. Mankind was finally reaching once more for the stars, and the red planet Mars was their first destination.

He toggled the microphone again. "This is Assembly Control. Clear launch apron. Zero-X moving into position."

Scott Tracy awoke twisting and shouting in the dark. It took several pounding heartbeats for him to realize where he was; recognize the scents and sounds of his tropical island home. Eyes closing in relief, he sank slowly back to the sweat-dampened sheets.

It had been a while since he'd had the nightmare, and even longer since it had been this frantic, this detailed, this real. But when he glanced over at the glowing red time-and-date display on his bedside table, it took him only a second to understand why.

Halfway around the world, the Zero-X was scheduled to launch today.

Scott lay there for a few minutes longer, concentrating on slowing his breathing. There wasn't any point trying to go back to sleep – it was 3:45 a.m. and the live telecasts were due to start in a little over an hour. The whole family had set their alarms for this and the living room would soon be a hive of activity.

The thought of facing it all made his stomach churn.

He made himself get up anyway, take a fast shower, haul on tee shirt and shorts. He had coffee brewed in the kitchen and was on the balcony with a mug already cooling by the time he heard the others begin to file down the hallway in his direction. "Tell me again why we live on the other side of the world?" he heard Alan grumble, fitting the words around a giant yawn.

"We don't," Gordon pointed out. "We live on this side."

Scott couldn't suppress a smile. Like him and their father, Jeff, Gordon had no trouble waking up no matter what time it was – and his sense of humor never seemed to take time off. Scott was convinced that this was one of the chief reasons his second youngest brother was walking now, instead of facing a life confined to a wheelchair after the accident two years ago that had almost taken his life.

The chatter dropped to a murmur as they all disappeared into the kitchen, and Scott's smile faded with them. He stared out at the horizon, willing the vast calm of the ocean to do its magic on his too-raw nerves. It wasn't working today, though. It didn't help that the clouds still lingering from a recent tropical cyclone blotted out most of the usually brilliant stars, making the water look as black and impenetrable as his thoughts.

Footsteps approached; he didn't need to look around to know who it was. Virgil leaned on the balcony railing beside him with a sigh, favorite mug in hand. Green, of course. "Morning," he said from somewhere deep down in his chest. "If that's what you call this."

Scott didn't want to answer. Didn't want to join the conversation, knowing what was coming. He realized he was gripping his own coffee mug too hard; consciously forced his fingers to loosen, his shoulders to lower.

Virgil saw it all, of course, because he knew. He was the only one who did. When he spoke, his voice was low, full of concern. "Are you OK?"

There it was. The train heading for him in the tunnel, headlights blazing. Scott took a deep breath. "I don't know, Virg," he said, honestly. "I don't know."

"This is Assembly Control. Radio-controlled Lifting Body 2 about to take up position. All fuel tankers should now retire to the specials area."

The long main fuselage of the Zero-X was parked now, perpendicular to the tower. Cleverly designed hydraulic rams held her up off the tarmac as she waited for the next stage of her assembly. A series of lights glowed green from his panel, and the Controller watched as the powerful rear lifting body, all wings and wheels, rolled out from its hangar to his right. The flat central portion slipped smoothly beneath the Zero-X's massive boosters, the main body lowering into place and locking with an audible thunk.

"Weather conditions for takeoff remain at go," the Controller announced. "Radio-controlled Lifting Body 1 about to take up launch position."

Everything was going exactly to plan, the equipment working flawlessly. The Controller wasn't normally one to risk jinxing an operation with premature confidence, but it was all going so well he couldn't help a small smile.

Right on schedule, Lifting Body 1's steel guide mechanism began to feed slowly out from the hangar.

"Are you ever going to tell them? Are you ever going to tell Dad?"

It wasn't the first time he'd heard those words. Scott didn't respond at first. He was standing outside reality, somehow, strangely disoriented – as if he'd scrambled his brain pulling too many G's. He realized belatedly that he wasn't prepared for this moment; hadn't known how bad it was going to feel.

Virgil was waiting. "The longer it goes, the harder it gets, Virg," Scott managed at last. "How do you think you'd feel, if you were him, and your son dropped something like that on you when it was too late to do anything about it?"

"That was the point, though, wasn't it," Virgil said softly. "You didn't want him to be able to do anything about it."

Scott shot him a look, but there was nothing on his brother's face but compassion and concern. He sighed, scrubbing his fingers through his thick curls. "Well, what would you have done, in my place?" he asked, a little more sharply than he intended. "Brought the whole thing crashing down? You know that's what would have happened. Dad… You know what he's like."

He turned, waving a hand to encompass the island and by extension, all it contained. "It was worth it, right? I made the right decision."

"Are you asking me or telling me?"

Scott bristled for a moment – then remembered who he was talking to. Remembered that no matter what, his closest brother, his best friend, would always tell him the truth, and always have his back. He was desperately glad at this moment for that understanding, that complete lack of judgement. Without Virgil, there would have been no one he could have shared this with, no one he could have anchored to. No one who could pull him back from the brink, now.

The moon had broken through the clouds; he stared at the patch of pale light glittering on the surface of the waves. "Dad had this whole thing set up in his mind for years, long before we knew about it. Like an engineering diagram. We were all vital components. He needed all of us or the ship wouldn't fly."

"Just like the Zero-X," Virgil said.

Scott couldn't respond. He felt like he was drowning, silently, although the ocean was a long way below his feet.

"This is Assembly Control. Phase One now completed. The Zero-X Martian Excursion Vehicle will be joining the main ship at Zero minus Five. "

The Launch Controller took a last look at Lifting Body 1, wheels folded down and locked into position. Then he hit the button marked "DOWN" on his panel. The circular control module immediately began to lower into the floor. It was time to have a last word with the Zero-X's crew before takeoff.

As he dropped through the bottom of the tube he was instantly surrounded by the purposeful chatter of the main control room. The three men waiting for him in the docked MEV looked remarkably calm, considering the magnitude of the journey they were about to embark upon. "Dr. Grant, Dr. Pierce," he said into the mike, addressing the two mission scientists he couldn't see. "Can you hear me?"

Receiving affirmatives, he faced the three flight personnel in front of him. "Paul, Greg, Brad," he said. "This is a tough assignment. If this mission is successful, you will be the first men to land on Mars."

He wasn't saying anything they didn't know, of course. But he felt he had to underline it like this, had to make sure they knew what this meant to everyone in the space program, not just to themselves. What it meant to him. Twenty years earlier, he might have been one of them.

There was one more thing that needed to be said. "This project has been the most costly yet devised by man." He saw the flicker of irritation in the mission commander's eyes…bringing up the budget at a time like this. He extinguished it with his next words. "However, the safety of the crew and passengers still takes top priority. Now is that clearly understood?"

Nods all around. The Controller took a last look at the men in front of them…and instantly hoped it wasn't literally that, a last look. "Away you go," he said, hoping he was concealing the lump in his throat. "And good luck."

"We're getting close now. Lifting Body 1 is in position. Now we're just waiting for the MEV, the Martian Excursion Vehicle. It will come out from the control building over there, and back into position to form the nose cone. And then the Zero-X will be ready for takeoff."

They'd turned up the volume now in the living room, and Scott's stomach clenched involuntarily at the sound of the news reporter's voice. "Hey, guys, you're missing the assembly," Gordon called out. "That's the best part!"

Alan snorted. "You're kidding, right? What about the liftoff?"

"Aw, I see really big machines lift off all the time around here. Enough power and you can get anything off the ground. Watching how it all goes together, though…that's something special. Like ballet, but with monsters."

"You sound just like Virgil," Tin-Tin said, the smile clear in her voice.

"That's it, Gordon," Jeff Tracy's deep voice chimed in approvingly. "That's the beauty of it. It's teamwork, taken to the nth degree. Each component has its function to perform, and together they are far greater than the sum of their parts."

On the balcony, Scott felt hot, scorching rage bubble up inside him, just for a moment…and killed it immediately, knowing it was unwarranted and undeserved. How alike he and his father were, where it counted. They'd even used the same analogy, minutes apart.

He glanced at Virgil. "You'd better go in."

"Are you coming?"

"In a minute. But go on, I don't want you to miss this."

Virgil hesitated for a couple of seconds. Then he reached out and squeezed his oldest brother's shoulder. "For what it's worth, Scott…"

Scott nodded, not trusting his voice. Then his brother was gone and Scott was left to stare at the black water and remember the one thing Virgil didn't know. The real reason for the decision he'd made, two years ago. The real reason he wasn't at Glenn Field at this very moment, strapped into that MEV, wearing the blue uniform of the Space Agency with the orange Zero-X patch on his sleeve. He'd told Virgil he'd sacrificed his own dream in favor of his father's. But that wasn't the whole truth, not even close.

He'd made a promise, a long time ago. A promise to the most important woman in his life – in all of their lives.

Promise me…you won't go to… sleep now, Scott. I'm…trusting you… to take care of… your brothers. Don't… let anything happen… to them.

He could still close his eyes and hear the howl of the wind, the rain beating down on the truck. His brother Johnny crying in the back seat – Virgil, forever the caretaker, trying to calm him. His mother's voice, saying her last words as he held his newest baby brother in his arms. Saying them to him.

Promise me…

Only Scott remembered this. And only Scott knew that when he had stood in that intensive care unit two years ago at the Naval Medical Center complex in San Diego, staring at Gordon's unrecognizably battered and broken body, he'd left the letter with the World Space Agency masthead on his desk back at his Air Force duty station in Russia.

The letter that had told him he'd made the cut. He was going to Mars.

But he'd promised. And a Tracy never broke a promise. Never.

"Will you look at that?" Alan's voice sparkled with enthusiasm.

"The excitement's rising here, folks. As you can see, the Martian Excursion Vehicle is now making its ninety-degree turn and will then reverse to dock with the Zero-X main fuselage. On board is the flight crew: Captain Paul Travers and his copilot Space Captain Greg Martin, and Space Navigator Brad Newman, who will remain with the main body of the Zero-X in orbit while the MEV makes the historic first manned landing on Mars."

"Look," Tin-Tin said. "There's the nose cone!"

The news reporter confirmed her observation. "What you're seeing now rising out of the tarmac is the nose cone, which will protect the crew of the Zero-X until she leaves Earth's atmosphere. After the reusable lifting bodies detach from the ship, the crew will jettison the nose cone and begin their journey to the red planet."

There was a long pause in the commentary. Then: "We have ignition! Ladies and gentlemen, the Zero-X is moving down the runway!"

It'll be over soon, Scott thought. Just a few more minutes, and it'll be over.

The Launch Controller was back in his element, now, monitoring the instruments for takeoff. He didn't realize he'd been holding his breath until the scattered applause broke out in the control room and he looked up at the monitors, seeing that the massive craft was clear of the ground.

"Central Control from Zero-X. Height, 20,000 feet. Airspeed, Mach One." Paul Travers' voice was sure and steady.

Everything was in the groove. He mentally ticked off the list. Next hurdle, successful separation of both lifting bodies, which would then return to the field on remote control. Then, nose cone jettison, and… Mars.

But the next words he heard over the flightcom were completely unexpected. Travers' voice held a very different tone now. "Base, this is Zero-X. Our control system is jammed. Nose is dropping. Ejecting nose cone."

What the—? After the first second of total confusion, the years of training snapped smoothly into place. He'd mourn the mission later…right now he had to get these men safely back on the ground. "Zero-X, what is your speed and rate of descent?"

It was Greg Martin who answered. "Rate of descent 3,000 feet per minute. Air speed Mach One point Four."

The Launch Controller spun his control unit to face the large map screens on the wall. He hit the switch and Zero-X's projected glide path extended out over the coast. "This is Central Control. Air Sea Rescue units, immediate launch. Vector 276 magnetic, range 172 miles."

"Central Control, this is Captain Travers. We are still unable to free the control system. Am ordering crew to eject. Repeat, eject.

"Roger, Zero-X. Do not eject until you are at 1,000 feet. Air Sea Rescue is on its way."

Now all the Controller could do was wait for the confirmation that the crew had made it out safely.

"Dad," John said suddenly from his screen on the wall of the lounge. "Something's wrong."

"What do you mean, John?"

"Zero-X isn't climbing any more. She's leveled off."

Scott raised his head, listening, on instant alert.

"OK, Dad, this is serious," John's voice again. "Zero-X has ejected her nose cone and she's diving."

"Can you find out what's wrong?" Gordon asked.

"I'll see if I can listen in."

Scott turned from the balcony rail, the tension in the room drawing him inexorably toward it. His adrenaline levels rose as he felt himself shift automatically into professional International Rescue mode. He could already feel the control levers of Thunderbird One under his palms.

He paused in the open balcony doorway, briefly meeting Virgil's glance. His brother, too, was ready to go.

"They've got some kind of elevator control jam from what they're saying," John was reporting back. "They can't fix it. Captain Travers has told Central Control he's ordering the crew to eject. Glenn Field is sending out Air Sea Rescue."

"What a shame," Tin-Tin said. "To get so close, and then have a malfunction like that."

"As long as the crew is safe, that's what counts," Jeff said. "Machines can be rebuilt, even a monster like the Zero-X. We're not done with Mars yet."

"Zero-X is at 1,000 feet," John said. "They're ejecting. Splashdown about a hundred seventy five miles off the coast."

"All the crew safe?" Jeff asked.

"Yes, sir."

The telescreen came alive then with video of the escape capsule bobbing on the waves. The news helijets had caught up.

So that's it. All this time, this was all I missed.

Scott felt suddenly, impossibly light, as if a load he hadn't realized he was carrying had lifted away. Ironic laughter bubbled up inside him, powerful enough to make him turn away quickly before his family could see.

But not before he'd caught Virgil's eyes, and seen the answer to his question.

It had been worth it, and he had made the right decision. He was exactly where he belonged.