It didn't get any easier, watching Rin die a third time.

Martin tried a different tack on this attempt. He scooped up the chronotanium just as the anime biker dropped it, shot his past self with the beanbag shotgun, and managed to talk Rin into driving to a nearby park.

He explained what happened to her, handed her the stone...

And a tree fell on her.

"That shouldn't be possible," BIRD said, as the little machine squinted into Rin's mechanical eye.

"Dying a third time the moment she takes the stone?" Martin asked, as he crouched down next to Rin's still form and closed her eyes. "You're right, that shouldn't be possible."

"Actually, it fits with a couple of theories I'm building about how time travel works," BIRD disagreed. "But that's not what has my circuits blowing. Look, this tree, falling in the direction it did, should be impossible. We're held on the ground by centrifugal force, it isn't real gravity. Neo Tokyo's spin should have made the tree fall in the opposite direction."

"BIRD, I've had it with whatever the hell is happening. What do I need to do to save her?"

"First, we stop and think for a bit. And as much as Rin won't remember it, you might not want to make her die over and over again as you try for the magical combination of events that keeps her alive," BIRD explained.

Martin nodded. "So, why does she keep dying?"

"My best working theory is that you can't undo the reason you picked up the time stone, I mean chronotanium," BIRD said. "And the reason you picked up the stone is to prevent her from dying."

"Wait, you're saying she has to die, or I wouldn't pick up the stone?" Martin asked.

"Pretty much. We could test my theory, but I'm pretty sure all you'll do is kill Rin over and over again, in increasingly absurd ways."

"Why absurd?"

"Her second death shouldn't have happened. Vehicles in Neo Tokyo have smart-assistants, and unlike people those robots don't suck at driving. Children can do laps across the Information Highway and be in absolutely no danger. Hell, a few of them are doing it now." BIRD pointed with its wing over at the highway they had crossed earlier. A group of school-aged children were having a race across it, and the hundreds of vehicles blitzing around them at hundreds of kilometres an hour all passed well away from the kids.

"I see what you're saying," Martin agreed.

"The first time she died, I get that. The green glow of the stone could have confused the transport truck's sensors. Possibly. It's extremely unlikely, but only in the way that occasionally a politician does something useful. But every time after, her deaths have gotten more and more absurd. Do it a few more times and we might see her get taken out by some lost space junk launched back in the 21st century."

"So you're saying fate is keeping her from getting the stone?" Martin asked.

"Possibly. But we really should try to narrow down the possible explanations, see if we can rule out some theories about how time travel works."

"So you're saying," Martin picked up the stone as he talked, and turned back to his bike. "All I have to do, to keep Rin alive, is keep her from getting the chronotanium?"

"That's a possibility, but-"

"But nothing, BIRD," Martin cut the little robot off with the click of the stone setting into the slot on his bike. He plugged in his phone, and changed the clock to ten minutes earlier. "Let's go."

"So, fourth time's the charm?" BIRD asked.

Martin was beginning to feel that having an animal sidekick wasn't worth the irritation.

Except, as it turned out, the fourth time ended no better than the third.

It went well, at first. Martin managed to blitz by and snag the case without dropping below sixty clicks, but before he could get away Rin hacked and disabled his bike, and his past self managed to put a beanbag round into his stomach from nearly half a kilometre away. By the time he got back up, Rin had gotten the stone, tripped on an open manhole, and cracked her head several times on the way down.

Martin only barely managed to escape with the stone while his past self was checking Rin's vitals. He stole his past self's bike again, and hoped the next time would be different.

It was. And it wasn't.

Rin died pursuing him across the Information Highway, never actually touching the stone. BIRD thought that was important, but if it knew why it didn't share.

The next two attempts ended just as horrifically. The one after that saw Rin die when her implants overloaded, something BIRD insisted wasn't physically possible.

"Her artificial eye uses less electrical current than either of your organic ones, and its battery is so weak a dead firefly would scoff at it!" the little robot said incredulously, waving those little wings and throwing a temper-tantrum over the absurdity of the universe. "Being struck by lightning would be more likely, even on an environmentally controlled space station that doesn't even have clouds."

BIRD was slightly relieved that, on their next attempt, Rin wasn't struck by lightning. Until Martin pointed out that the truck that killed her belonged to a company called 'Lightning-Quick Instillations'.

Martin, at this point, wandered over to a nearby bench and buried his head in his hands. His hands began to shake against his face, quickly joined by his whole body shuddering once. And like an earthquake breaking a levee wall, Martin began to weep.

"Fuck," he managed to mumble as his hands turned damp and sat up to shake them off.

"Existential crisis?" BIRD asked, as it hopped over onto the bench next to him.

"I can't save her," Martin said. "Why the hell can't I save her?"

"In fact, every time you try, it seems to make things worse," BIRD added. "Kinda suggests you should have stopped after the third attempt."

"Are you saying I shouldn't have tried to save her?"

"I'm saying you should stop and think, before you try again," BIRD said, and it looked rather pointedly at the stone in Martin's hand. "After all, you have time."

Martin looked at the glowing ball of green in his hand. "I have time," he agreed. But there was something about how the little robot said it, something in the intonation, that left Martin feeling like he didn't understand anything about those three little words.

"That isn't hyperbole, you twit." BIRD very deliberately hopped up Martin's arm, across his shoulder, and whacked him in the back of the head with its wing. "We could quite literally spend a year, right here, planning out our next move, and then travel back in time to enact it. About the only proviso is you can't go more than two years back in time."

"Why not?"

"Because the station was only built two years ago. So far, time travel will only put you roughly where you were, relative to where you are now. Which you should be grateful for," BIRD said.

"Why is that?" Martin asked.

"How does someone who's been living in an interplanetary civilization his whole life not know about drift velocity? Look kid, here's some grade-school physics for you. Everything is constantly moving. Which means if you went back in time five minutes to exactly where you were five minutes ago, this whole space station would be about four thousand kilometres away from where you appeared. Somehow, time travel seems to involve keeping you in the same place relative to where you were when you jump. And it might be by sheer stupid luck or plot convenience, but you managed to avoid jumping into the back of a tanker truck or crashing into another vehicle every time."

"Okay," Martin said, nodding.

"So you can't go back in time and kill Hitler, unless you took a ship back to Earth first. By the way, do you want to go back in time and try to make everything better?" BIRD asked.

"Judging by my results so far, I'd make a giant hash of it," Martin said.

"Now you're learning," BIRD said, and the condescending approval in the little robot's tone left Martin wanting to shove it beak-first into an electrical socket. "So, what we need to do first is figure out what the mechanics of time travel are, or at least what the author of this idiot tale picked."

"What do you mean?"

"Up until five minutes ago, time travel was so theoretical the only people working on it were science fiction writers. So you and I have the only experimental evidence to work out how it actually works. And since comparing your cognitive abilities with mine is like comparing a fungus to Issac Newton, it means I'm the one stuck trying to figure this out."

"I may shoot you, BIRD," Martin warned. "But you're wrong."

"Unlikely."

"Remember, Rin said I had met her before."

"I've been trying to avoid that," BIRD admitted. "Partially because, given how many times she's died already, it might be a good idea to keep ourselves and the stone away from her."

"Well, what if we went further back into time? Like a day or two in the past, and ask her about her work on time travel?" Martin asked. "The stone would disappear, since it needs to go back to wherever it was then. We'd have lots of time to try and figure out not only how time travel works, but also why she said we'd met before."

"That's..." BIRD paused, as if it had encountered an error in its code. "Not a bad idea. I take back what I said about comparing you to a fungus. More like a houseplant, or a jellyfish."

"Huzzah, I moved up in the world," Martin said drily, sitting up and taking out his phone. He changed the date to eight in the morning, two days prior, and plugged it into the bike. "Where do you think she was, two days ago?"

"Working, probably. Unlike a billionaire mercenary, most people have to work for a living," BIRD said.

"Fair enough. Where did Rin say she worked?"

"Wow. You're actually using me as a Backup Information Retrieval Device. Not a plot twist I was expecting," BIRD replied, as it tilted its head. It opened its beak, and projected a little hologram of Rin into the air in front of it. Rin was smiling, just about to throw her leg over her motorcycle. "My lab. Physics Department, Wiki College, in the IPv4 district," Rin said. "It's a forty-minute ride if we take the Information Highway," Rin's hologram said.

The hologram disappeared, and BIRD closed its beak. "Got it," Martin said. "Wiki college."

Martin fished the stone out of his pocket. The damn thing seemed to be glowing brighter than it had before, enough that he was tempted to wrap the thing in a towel if he was going to try to hide it again. "Well, hopefully this works."

"Hey, if you don't succeed, we can always try again. So the girl you're trying to save can die over and over, in increasingly comedic ways," BIRD said.

Martin set the stone in place, and started driving. BIRD only barley managed to cling to Martin's shoulder, as they took a turn back onto the information highway, and started accelerating.

Light flashed, and for a sixth time in the last twenty minutes, Martin travelled back in time.

Though, with how far back he was travelling, would that make it the first time?