Coleman snorts. "Ye've done all these figure studies of her, and you ain't figured out she's alive?"

Gently, he grabs one of Ailee's paws and guides it to the freshly burnished patch. "She's only a baby right now. Still comin' into her own. Still weak, still needs protecting. She's the reason the Flood came at us so hard, is because I wouldn't give her Sasha. Feel her cooin'? She knows it's you.

"This li'l bunsen burner's the whole reason I'm headin' to the Heart. Rather, to Terminus Station. Here, lookie at Gramps' wrench, it's got some pictograms of the history. See that li'l figure there? That's the First Engineer, and the bigger figure next to them's the First Train. There're whole crews of philosophers on other trains doing the mindwork of figuring out what happened, but when the two met, s'was like a spark. The two connected, an' each became something more than they were before.

"And ever since, trains've only been able to hatch at Terminus. We're not sure whether it's the heat or the memory or such, but for Sasha here to fully come into her own, we need to reach Terminus. There, she'll finally become an engine in her own right, and I'll probably be subsumed in the transformation."

He says it frankly, like it's just a fact of life, but there's just that little edge of doubt crinkling in the corners of his eyes. "At least, I think so. Maybe subsumed's the wrong word. Assimilated? Jackdaw's the one to know the fancy vocab about it. Point is, I'll take on some aspect of Sasha, and she'll take on some of me. We'll merge a bit more. It's a privilege and a heavy burden, because what I'm doin' now is going to influence Sasha for the rest of her life, and that's gonna be centuries past when I'm long gone."