This time Thor was very careful to go exactly where and when he meant. He arrived inside his ship, the night before Thanos came, inside the room where he and Loki were talking. They were standing side by side at the window. "I just… I can't believe it," Loki murmured.

"Mm." But his past self was not listening; Thor could tell.

"I mean… they told us Asgard was eternal. Do you remember?"

"Mm."

"All those years. All those stories. And now it's gone. The sun will never rise on Asgard again."

His jaw dropped. "There! There it is!" he shouted, and clambered out from his hiding place.

Both of the past Odinsons whirled to face him, squared up to fight. He ignored that. "There – listen, that's the words. That's exactly the words! Before he kills you!" In his excitement the explanation was all tumbling out of him in pieces, and of course nobody understood.

Past-Thor took charge. "Who are you?" he said, irritably. "And who kills whom? What are you, one of the madmen?"

Loki looked at him. "The madmen?"

"Heimdall made space in his camp for all the children and the sick and the mad," Past-Thor explained. "So although we didn't manage to salvage much of the army, we do have plenty of them."

He felt his face pull into a wince. "Was I really so intolerant?" he wondered aloud. Then assured Loki, who was staring at him: "I don't mind children, or sick or mad people. I play online with them all the time."

"What- what are you," Past-Thor sputtered again. "I don't understand."

"Yes you do," Loki said calmly, but without lowering his knives. "He's saying that he's you. From the future, presumably."

Thor nodded. "Exactly! You really always were the smart one."

"I'm not saying I believe you." Loki turned to his brother. "Make him prove it."

Thor laughed. "Not all of us are as paranoid as you, brother. I can't prove it; I don't have any signs or signals with myself. But I do remember yours." He performed the action that Loki had taught him during his visit into childhood, and waited.

Loki relaxed. "All right, Thor, stand down," he said to his brother. Past-Thor relaxed – reluctantly. He still looked wary and grizzled and completely ready for battle.

"Chill out, my friend," Thor advised his past self cheerfully. "It's no good to live like that. You've got to stop and smell the roses every now and then. Or whatever flowers they have out here."

But Past-Thor did not chill out. In fact he ignored him completely, and spoke instead to his brother. "You're telling me that this," he said, "Is what I become – and that you're all right with it?"

"I'm not saying I'm all right with it," Loki said patiently, "Only that he must be here with my blessing; he'd have no way of knowing that gesture unless I taught it to him." And then, proving once and for all that Loki really did thrive on cruelty and the gratuitous infliction of pain, he added: "But of course I'm not all right with it. He's lazy, and an idiot. You're not nearly that bad normally." Then, turning to him: "Did you perhaps have a head wound or something… um, brother?" A smile so insincere and patronizing that he wondered if it might be a joke.

"I'm- I'm not-…" Thor swallowed. What could he say? He was lazy, if lazy meant sitting in his room wanting to do very little and doing nothing that he didn't want to do. And as for being an idiot… he disputed that, but it wasn't a name Loki hadn't called him before He shrugged it off. "No wounds worse than the usual. In any event, we don't have much time. Thanos will come here tomorrow and destroy this ship; we have to hurry. I need your help."

Past-Thor snorted. "Someone is coming to destroy our ship... and you need our help? Don't you have that backwards?"

Before Thor could answer, Loki nodded and agreed with his brother. "He's right. You just said we're in danger here - from Thanos. So why don't you help us? Go back in time another few decades, and kill Thanos in his cradle. I can assure you he deserves it."

Thor shook his head. "It doesn't work that way."

Loki seemed to be losing patience with him. "Well you're here, Thor, so there must be something you can do."

Past-Thor had no patience at all. "Don't call him that! I am Thor!"

Loki hissed. "Seriously? Fine." Turning back to him. "You are hereby Bearded Thor for the duration of this conversation. Now sit down, Bearded Thor, and tell us what happens. Tell us everything."

Thor told them everything. Everything. His voice was hoarse by the end. Both brothers looked thoughtful, but of course it was Loki who finished processing first. "All right." Loki rose, stretched his legs, and went to pour some water. "You really did come from the future," he said.

"I did."

"Using... that getup." He gestured vaguely. "Suit, particles, wristwatch."

Thor nodded.

"And you did it because I said something strange to you."

"Yes. You said: the sun will shine on us again. What did you mean?"

Loki let out a slow breath. Muttered under his breath for a while, talking to himself, frowning. "Well the obvious answer," he said slowly, after a long time, "Given the conversation we were having when you arrived, would be that I wanted you to go back in time. I'd just finished saying that Asgard would never see another sunrise going forward, and then I told you we should go and see the sun. Clearly, if I'd known you had the ability to time-travel, that is what I was directing you to do."

"But I didn't have the ability to time-travel, so how would either of us have known that?" Past-Thor said, and exactly the same moment Thor asked a much more basic question: "Why?"

Loki opted to answer the simpler question first. "Why did I tell you to go back in time? Oh, I don't know." Nasty and sarcastic, suddenly. "Perhaps because I'd just seen how utterly prepared you were to sacrifice my life." He stomped his way across the room as he ranted. "You left me to Ragnarok. To die in it. When I showed up on this damned ship you were honestly surprised to see me – weren't you. Don't lie." He looked from one iteration of his brother to the other. "Either of you."

Thor looked at his past self. Winced and shrugged.

Past-Thor did his best. "I did think it possible that you might have made it," he said. Looked for support. "Right?"

"Oh, yes," Thor nodded big for emphasis. "It was possible. I mean, we know it was possible, because here you are!" He tried a smile. Come on, brother. Look on the bright side! You're alive. (For the moment.).

"You meant for me to die," Loki insisted quietly, "And you were fully ready to go on without me. Weren't you." He stopped dead and looked Thor square in the eyes.

Thor tried not to look at his past self again; exchanging glances like that made them look so guilty. "To be fair, it was your third time dying in recent years," he pointed out. "I'd come to sort of expect everything to-"

"We had no choice, Loki." The disaster was still fresh in Past-Thor's mind; he had risen and was moving around in his agitation. "You know as well as I did. We had no other way."

"You thought up the suicide mission," Loki reminded, pacing just as restlessly, "And meant me to execute it, while you went on your merry way. Of course I didn't expect you to journey through time on your own initiative to save my life now."

"Loki…" He wasn't sure how to deny it.

But Loki's gaze was fixed on his other brother. "The only question, though, is how would I have known you had that option?" he murmured. "We've never discussed time travel. Never even hinted at it."

Past-Thor slapped his hand against the wall, irritably. "Fuck, Loki, I don't know. I don't know what you know. Maybe he's lying. Or maybe it meant nothing – maybe you took a head wound during the battle, and started spouting nonsense. It wouldn't be the first time."

"No," Thor insisted, firmly. "Your actions were deliberate. They looked, they smelled, like a Loki plan of old. Trickery and misdirection of some kind."

Loki shook his head. "My plans of old tended to work, Thor."

"Maybe this one did. Or would have, if I'd understood you better. I don't know."

"Mm." Loki altered the path of his pacing a little, so as not to collide with Past-Thor. Then, suddenly, he jerked and pointed. "Sh! Did you hear that?"

Thor whipped around – "Did I hear what?" – but there was nothing there. When he turned back he bumped smack into Loki, who was now right in front of him.

"Ow!" Loki rubbed himself, brushing spilled water from his clothes. "Watch where you're going, Bearded Thor. You take up a lot more space than you used to."

That was so unjust – Loki had bumped into him, not the other way around – that it took Thor a moment to formulate a response. "Loki…" Past-Thor warned, but it was already too late.

Loki's hands opened with a flash of blue. There was a billow of dark smoke... and he was gone.

Thor turned to his past self. "What the fuck?"

His past self was livid. "I don't know – it looks to me like Loki just used the Tesseract and disappeared on us," he snarled. "After deliberately colliding with you. Did he steal something?"

"Steal what?" Thor patted himself down. "I didn't bring a wallet, I have nothing here to-" His bracelet was gone. "Son of a bitch."

TBC.

So. I've been trying to understand the time travel logic used in Endgame (thank you Rynfinity for helping!), and I think I understand how it may work, but it's entirely possible I am wrong. I think what I have comports with rules that aren't foreclosed by canon, so, I'm going with it.

Somehow though, during our conversation the story became longer (damn you Rynfinity for enabling!), and with the possibility for a hint of crack at the end, so I can no longer promise it's going to end in one or two more parts. I'm going to try and do it that short. But we'll see.

Let me know what you think!