[ William keeps Robbie in his periphery—his smile isn't the kind meant to be acknowledged head-on—until he speaks, then turns a half-step toward him. To see how much weight the words have. The closest he's come to despair is the days of isolation, the feeling of everything around him slipping away.

Right now, though, he's just the slightest bit excited. ]

Escape velocity. [ It's mostly a joke. Mostly. William rocks back on his heels, trying to imagine not why but how the symbols were written. Urgently? Ceremoniously? Are they studying graffiti? The hand that put them there, was it soft or rough? ] A chemical equation... [ He shrugs, one armed, raises his eyebrows. He's not convinced himself. ]

I think the placement's important. It couldn't have been easy to get up there. [ A hesitant pause, then he shoots Robbie another glance. ] What would you want it to say?