he who hesitates is toast

"That's what they - when he disappeared, when he didn't come back, that's what they - we - decided the public should know, but you - I thought you - I didn't realize you didn't --"

He's babbling, he realizes, as he hears himself, and makes himself shut up for a second.

"After the fight. The Infinity Stones, from the gauntlet. They had to go back, I guess, to the points in time where they'd come from, or it'd screw things up somehow. They used Pym's particles, from long-ago research; Scott was the one who knew about them, and they used the first batch to go back and get them in the first place so they could use them to undo Thanos's snap..."

He draws a slow, careful breath. "But they had to go back. Which meant someone had to take them. Steve volunteered; of course he did. But it also meant - it meant he could, he could go back to, to before, when he was still on ice, when Peggy..."

He trails off there again for a moment, then whispers, "He asked me what I thought. We talked about it. And about Sam. About the shield."