This is set close to the start of my AU, before the war starts, i.e. after Reconstruction but before Mission One.

I wrote my own prompt for this one, in Disaster Ray, where there's the following throwaway comment: "...talking about climbing Boomerang. That was the route he and Mark had put up, the first summer, before the war had started for real, on the cliffs down by -"

I had no plans for it at the time, but at some point I put two and two together and realised just how early that was in their friendship, even earlier in their commander/second relationship, and that Mark probably wasn't Jason's first climbing partner.

Many thanks to my son Dan for beta-reading and tweaking the climbing stuff.

I can only name one real rock climb. It's called Boomerang Gully :)

Boomerang

"So when do we get to climb something hard?" Jason abseiled to the gym floor in two easy jumps and made a show of looking for the next route. "That's it?"

He knew Mark was slower than he was, and only belatedly considered how badly Tiny was struggling, that Princess had fallen off the overhang twice already, and that Keyop couldn't even reach the starting holds on the last three routes.

"For this wall, that's it," their instructor agreed. "I'm going to suggest that you - both of you - go put in some work on the cliffs."

Mark had landed neatly alongside him. "Cliffs?"

"Down on the coast road," Jason told him. "Plenty of seriously hard -"

He stopped. The instructor was nodding approvingly. Mark looked interested. And Jason realised that he hadn't just been set up, he'd volunteered for the damn job.

.

Two days later saw him driving down the coast road, back seat full of climbing equipment and his commander in the passenger seat. Jason didn't want to be here. Really didn't. And Mark seemed completely oblivious, making cheerful comments about the good conditions, calm winds, dry rock and blue sky.

"Tide's more important," Jason said shortly.

"It is?"

"We abseil down from the road level. Best climbs are on the lower cliffs. The top's all easy stuff. Unless you want to start there?"

Mark didn't rise to it. "If you want an easy practice route first, that's fine by me."

The worst of it was that he recognised the tricks. He'd used them himself, back when he'd been in command and Don had been desperately trying to show the senior staff how much better he'd be at it.

Don, who he'd left to die on Mars.

He almost missed that they were approaching the parking spot: a wide point in the road with space for three or four cars up against the cliff and another couple on the other side. He'd been strongly tempted to pull up there and see what Mark did when faced with eighty feet of air when he opened the car door, but he resisted the urge. They had to work together. No, he'd play nice and take the inland parking spot.

Mark said nothing about the somewhat less than smooth stop. He just got out of the car, hefted his share of the climbing gear, and followed Jason across the road to the top of the climbs. The abseil bolts were older now, weathered rather than shiny, but the weather and tide were the same as they had been the very first time they'd come here, on the ISO selection camp, two years ago. Day four, it had been, and he'd already known Don was the man to beat. Don, as usual, had been making sure everyone knew what a skilled and experienced climber he was, and Jason had decided not to share that his entire climbing experience consisted of the two stories of brick wall below the window of his room at the children's home in Melbourne.

It had turned out that climbing vertical brick walls in the dark with no equipment or rope was better training than he'd expected.

"I said, which do you recommend?" That was about as exasperated as Mark got, and Jason wasn't in the mood.

"Pick one."

Instead, his commander grabbed his shoulder, swinging him round so they were face to face. "If you don't want to do this, say so now. I'm not climbing with you unless you're focused on it. We do this properly or not at all. Which is it?"

Just tell him, his subconscious said. He'll understand. Climbing here was something you did with Don, and Don died on Mars.

He'd rather eat ground glass.

"That one," he said, pointing to the third one along. "Doesn't matter which one you drop down for the climbs, but it's the smoothest abseil. Unless you want to top-rope?"

Mark actually rolled his eyes. "Is that it? You think I've never climbed except on a wall?"

"Well, have you?"

"Yes, and in conditions a lot nastier than this. Let's say I'm not used to climbing outdoors without gloves."

Jason didn't know what the significance was of climbing in gloves, had never done so, and sure as heck wasn't going to admit it. Instead, he threaded the abseil rope through the loop on the bolt, slipped his harness on, and clipped himself in. Mark could go second.

He'd not been down here since Mars, and as he stood at the bottom, for a moment the figure dropping smoothly down the cliff could almost have been Don. Similar height, hair colour, damn irritating superiority complex...

Don had been a darn good climber, too. Better than Jason. But if Don had realised that the skill gap between them was closing, he hadn't called a stop to their climbing trips. They'd been up most of the routes along here.

Mark had never been up any of them and probably didn't know where to start - the guidebook wasn't exactly published and Jason certainly hadn't made an effort to show him where it was. Still, he resisted the urge to suggest Mark tried soloing one of the really slimy ones and instead pointed at the left hand end of the rocky platform they stood on, ten feet above the sea at the current low tide. At high tide it would be well underwater.

"Did those nasty conditions include sea cliffs?"

Mark didn't blink. "No."

"Then let's start with something easy while you get used to seaweed, barnacles and dried salt."

His commander nodded. "Sure. You lead first?"

He couldn't exactly say no, though he'd much rather have watched Mark's first attempts from below. So he gritted his teeth and picked a good starter route with a variety of wet handholds and finger-tearing barnacles, not to mention the surprise mini rockpool ten feet up, and did what an experienced leader was supposed to do: pointed out the hazards and the tricks as he reached them. Once back at road level, he set up the belay so that he had at least some view of what was going on below him, and called, "Ready!"

"Take!" came from below in response, and Mark headed up towards him almost before he'd had a chance to take in all the slack. Perfectly proficient. Not as good as Don. Not lying about experience not on climbing walls. Smooth enough, good enough, doing all the right things, safe, friendly...

He wasn't Don.

And that's not his fault. Are you never going to enjoy climbing again, just because Don's dead?

Maybe, maybe not. But at least he didn't have to hate it. Conditions were perfect, and this was as good a way to learn to work with his new commander (now that he did hate) as any.

They worked their way steadily along the climbs from left to right. Geology had scaled them from easier to harder in neat stages. Perfect training ground for potential new ISO recruits. Perfect testing ground, now, for G-Force training. If a little easy, for most of them. The harder climbs were further to the right, rising to a promontory which was higher than the road. Further to the right still looked to be even harder, not least because the base of the climbs was beyond the rock shelf so there would be nothing to stand on. They'd not considered those, not beyond 'maybe next year'.

One in particular, the last obvious line starting from the rock platform, had been a magnet for the better climbers since the first time they'd come down here. To Jason, veteran of a crumbling brick wall and not much else, it had meant nothing. It had taken Don standing there with him at just the right time of day, with the light picking out the crevices and ledges, to show him the route curving up to the left and then over to the right to beyond the rock shelf, with the crux up a horizontal overhang with a sheer hundred foot drop into the waves below.

They'd been planning their attempt on it for the whole of that last summer. If the Mars mission had been a couple of days later...

So of course Mark noticed it, stood looking at it, squinting at it in the rather less than perfect light.

"How about that one?" he asked.

"Never done it," Jason said shortly.

"Has anyone?"

"Dunno."

"I thought there was a list?"

"It's not on the list." Don had had the entry all ready to go, full route description and all. Even the name.

"Shall we try it?"

He almost said no out of pure reflex, but that would mean an explanation he wasn't ready to give. And someone had to climb it first.

"Let's give it a go."

Maybe Mark would have asked if he wanted to lead, if he'd had any idea that it had special significance. Almost certainly he'd have agreed if Jason had said something. As it was, he was clearly a more experienced climber, had apparently been trained from birth to go first at just about everything, and Jason let him get on with it.

Mark moved smoothly and easily at first, straight up for a short way, then across to the right. He slowed as he approached the point where he'd go out over the water, which corresponded with a particularly smooth section of rock before the overhang crux.

Even the move before the crux looked hard: out of balance, with especially tiny, outward-sloping holds. The only saving grace was that they were too high to ever be covered by the tide, and the warm, calm weather had long since dried any sea spray.

Mark paused at what looked like the last secure location, placed a nut, and considered it. "See any more good spots?"

Jason bit back the sarcastic response about expecting to need it. Given what he was about to try, Mark might well think that he was about to come off. Much as he'd have liked to see his commander taken down a peg or two, that didn't extend to a crashing leader's fall onto dodgy protection. He squinted at the rockface, remembering what Don had said he planned to do.

"Six inches higher in the same crack? No, wait, a foot to the right - is that deep enough?"

Mark shifted his weight, chalked his fingers again, and felt for a crack he surely couldn't see. "Yeah, that'll do." A second, larger nut, a longer sling, and he had something rather more likely to hold a fall. That done, he chalked both hands again and checked that the rope was running freely. Jason did likewise. Friction through the protection would give him no chance at all.

"Climbing!" Left hand up, right hand up and out, feet up onto those marginal friction holds, and he extended everything, reaching over the edge of the overhang for the only available handhold.

Jason didn't recognise the expletive, but the significance was obvious. He took in slack as fast as he could, but nothing could have prevented Mark's ten foot drop to slam into the rockface.

"Okay?" he asked, more for form than from any real concern. Mark had already found hand and footholds and was scoping out his route back onto the climb.

"Sure. Climbing." There was annoyance in the tone. One thing he and Mark shared - Don had, too - was a genuine hatred of failure.

He was back to the secure stance in a couple of minutes. Checked the protection - which should be safer now than before he'd fallen, since it hadn't come out - and called down.

"How far short was I?"

Jason considered the chalk fingerprints on the rock. "Couple of centimetres? Maybe three."

He couldn't see Mark's expression, only the determined set of his shoulders as he chalked up again.

"Climbing!"

This time he shifted on the friction holds, getting every last millimetre of height available, and went for the overhang with everything he had.

He hit the rockface harder, and took longer to recover. A lot longer. Jason was just starting to worry when he glanced down.

"Slack."

Jason said nothing as he lowered Mark the last holdless ten feet to the ground.

"You were close," he said as the other unclipped the rope from his harness.

"Not close enough." Mark stepped back, considering the chalk marks. The second was maybe a centimetre higher than the first. "It's a decent hold if I can get there."

"Another friction hold before you jump?"

"There really isn't one. That rock's much smoother than the rest - you can see where the colour changes, it's in line with the front of the platform here. Catches the weather differently, maybe."

He looked sideways at Jason. "You're taller than me - want to give it a try?"

He wasn't sure he did - for all his needling of Mark, he'd never attempted an overhang that you'd even consider calling a roof, or one of any type which wasn't on a climbing wall, and their height difference was maybe the three centimetres Mark had failed by. So even if he managed to replicate what Mark had done, he'd just barely make it to the handhold. Then he still had to get round the overhang itself. It was another three feet vertically to the next possible place to put in some protection. If he failed before that point, he'd be falling faster and harder than Mark had.

But he wanted to walk away even less.

.

The route up to the crux wasn't as easy as Mark had made it look, and Jason found himself glad to have watched someone else tackle it first. Don had always said that leading was harder for more reasons than just how much further you fell if you got it wrong. One of them was having to place protection, normally. Jason didn't have to do that either. This was as easy as leading a new route got.

Still, he suspected he was slower than Mark to the crux. Up close it looked harder, if anything. The two tiny friction holds for his feet were almost invisible, and the overhang smooth and featureless. He was glad of the chalk fingerprints Mark had left, and that he'd made a mental note of exactly where they were in relation to the invisible hold above.

Man, that was a long way. And smooth. And he didn't fancy the fall. He checked the protection, more as a procrastination aid than because he didn't trust it. Mark had fallen hard onto it, twice. If anything the problem was going to be recovering it.

"Don't wait too long," Mark said from below. "You're not getting any fresher."

No, nor any less nervous. Jason said nothing, checking one last time that the rope was still running freely. Time to go for it.

"Climbing," he called, replaying the exact sequence of moves in his head for one final time. Right foot, left foot, and reach...

Half way through the reach he knew it wouldn't be enough. Not quite. But his direction was perfect, and if he could just find a fraction more upward momentum from his right foot against the rock...

The fingertips of his right hand hooked onto the tiny ledge, and Jason pulled as hard as he could and swung his left hand higher still. Where was that crack? He couldn't have missed it! He flailed blindly, felt something, and jammed his fist into it sideways.

Oh man, I hope I can get out of this. His right fingertips were starting to slip, his left hand was held in place by friction, and his feet were in mid-air. Jason gasped, swore, and swung his right foot round and over the edge, and found something approaching a hold. Every angle was wrong, but somehow he levered himself upwards to a position where he could see a good hold, one you could hang off all day, just a couple of inches above his right hand.

With a final gasp, Jason threw himself upwards, grabbing for the hold. Almost missed it despite everything, but then it was there, solid in his grasp. He could pull up on it, bring his left leg round the overhang, free his left hand, and keep going upwards to a crack where, finally, he could attach himself to the rockface and let his fingers relax. He'd done it.

"Jason? Talk to me." Mark actually sounded worried.

"I'm fine, he gasped. "Give me a minute."

"Take as long as you want. When you move, it's ten feet to the top, via the big crack rising left."

Ten feet to actual flat clifftop? Jason looked up, only now realising that his left hand was bleeding freely. Maybe that was why Mark had mentioned gloves. In any case, he wanted off this climb right now.

"Climbing!"

The last ten feet was easy, or at least felt that way given what had come before. Jason rolled over the edge in a way which would have made their instructor wince, and lay on his back, eyes closed and feeling the sun beat on his face.

I did it, Don.

His bracelet pinged, and Jason brought it to his face with a groan. His shoulders were going to hurt tomorrow. Heck, they hurt now.

"I thought this was easier than shouting," Mark's voice said. "You okay to bring me up? I might, um, need a tight rope on the overhang."

With nobody to see, Jason allowed himself a smirk. An admission that Mark couldn't do it. Even if it was mostly down to height, that felt sweet.

"Sure. Give me a minute to set up a belay." There was an unused bolt in the rock here. Putting it in had been the last thing he and Don had done, the final time they'd climbed together. They'd left it and walked back to the car, talking about how the forecast was good for Wednesday.

Wednesday morning they'd launched for Mars. Don hadn't come back.

Jason swallowed, gave the bolt a quick and entirely unnecessary pat, and tied off to it.

"Ready. Tell me when you need that tight rope."

"Will do. Climbing."

With the edge of the overhang in the way, Jason could see nothing. He kept the rope just barely taut, not pulling, and it came in much less steadily than he'd let it out the first time for Mark to climb first time round. Freeing jammed protection was a pain. Admitting you couldn't free it, sufficiently embarrassing that the pain was worth it. Jason sat in the sun at the top of the cliff, listening to grumbling from below him, occasionally learning some new words that were either Polish or Russian, and letting his instincts tell him how much slack he should take in. Since the grumbling wasn't about that, it probably wasn't too far wrong.

He could, he realised, really spoil his commander's day at this point. With all the protection below him removed, if Mark missed the hold above the overhang, he'd be left dangling below it. From there, the only option would be for Jason to lower him into the sea.

Tempting. In some alternate fantasy world where they didn't need to trust one another without hesitation.

"How's it going?" he called down, not on the bracelet since Mark was surely using both hands right now.

"Nearly there. Remind me to be lighter next time I fall."

"Or just don't fall?"

"Yeah, yeah. Come out, you..." There was a sudden sharp tug on the rope, and Jason braced himself. Of course, if Mark landed in the sea all by himself, there wouldn't be much he could do to prevent it.

"Got it. Last one." There was a pause. "I won't get close carrying all this."

He'd forgotten that - he suspected they both had. Mark now had a belt hung with slings, nuts and karabiners, and even lightweight modern tech wasn't zero weight.

"You want to abort?"

"Rather not. Rather not go for a swim, either."

"Tight rope?"

"When I say." Sounds of shifting weight, accompanied now by the clink of the hardware he was carrying. "Okay, let's do this. Tight rope now."

There was a grunt of effort, and Jason took the rope in hard and fast. Carrying that lot, Mark could well need an extra ten centimetres, and the only place it was going to come from was him.

One hand appeared, fingers locked onto the first hold. Jason kept taking the rope in, wary of it running over the edge of the rock. If he tried hard, he could probably pull hard enough to cut right through it, which wasn't what he was aiming for at all. A second hand, using a rather more orthodox hold than his fist jam. A right foot over the edge, and a far more controlled move round the corner and up to safety.

It was a gratifyingly long time until Mark called for slack and started to remove the last piece of protection on the climb. This one hadn't held a fall, and came out easily. He took the last ten feet slowly, carefully, and completely by the book, eased himself onto the clifftop alongside Jason, and sat and gasped.

Jason said nothing, just started to unfasten the belay to avoid the awkward silence. That only bought him a minute or so, but he needed less than that. As he turned back from unclipping from the bolt, Mark was on his feet, stepping away from the edge and untying himself from the rope.

"Now that," he said, "was a lot harder than it looks. And it didn't look easy. Nice work."

He couldn't think of anything to say except "Thank you."

Mark opened his mouth, did a double take. "Jason - your hand!"

It hadn't hurt until now, but suddenly he was aware of every missing scrap of skin, and that he was dripping blood, and that it stung like all hell.

He managed a rueful smile. "Maybe I should have been using those gloves."

"But you don't -" Mark stopped. "Jason, how much climbing have you done which wasn't on a wall?"

He could lie, or dissimulate, or he could come clean and see how his new commander reacted to having a second who didn't have over a decade of perfectly scripted training behind him. And, actually, he did want to know how Mark felt about it.

"Apart from these cliffs here? None."

There was silence. Then Mark said, "So you've no experience of hand jams, or big overhangs. None at all."

"Nope."

"Damn, you improvise well. But..." and there was a long enough pause that Jason turned to look at him, "you need more technique."

"I guess."

"You want someone who isn't me, go ask Anderson. Or we can come back here in a couple of days when your hand's healed." He grinned. "I'm guessing once you've spent ten minutes with Youtube, you won't need me or anyone else to demonstrate. But you will need someone on the other end of the rope while you try it out."

"Yeah," he said. He could have some random climbing instructor or he could have Mark. To his surprise, he was aware he'd rather have Mark.

"So," said Mark, beginning to coil his end of the rope, "if you're done bleeding, let's tidy up here and get back. What's it called, by the way?"

"I know what I'll call it," Don had said as they stood side by side. "Boomerang."

Jason had frowned, and Don had given him one of his long lectures on how the leader of the first ascent got to name the climb, and what appropriate names might be for a line with a massive great curve in it, and made an entirely unfunny joke about needing an Australian involved.

"Boomerang," he said, and only then considered his commander's chosen personal weapon.

Mark laughed. "And when we put up the direct line, it can be Shuriken? I like that."

Jason blinked. Direct line? He'd not been sure even the easiest line was climbable. But Mark had seemed entirely serious. And he'd done something Don would never have done in that situation.

He'd used 'we'.

He flexed his hand, considering the damage. "Let's do that. Should be healed enough by Wednesday."

Mark peered at the cuts. "Maybe Thursday. Shouldn't be longer than that, not now your implant's upgraded."

"Thursday, then."

They headed back along the clifftop to where the car stood waiting, and Jason realised he'd enjoyed it. Not only that, he was looking forward to the next time.