Ay, and there’s the rub. Strange makes a thoughtful noise, a tut against his teeth, as they start climbing one of those long stairwells (it’s too long; it twists and winds more than it ought to, the storeys in this building climbing taller than it looks from the outside, but that’s par for the course at the Sanctum).

“That’s the million-dollar question, isn’t it?” he says. “I’ve been pretty agnostic, since we can’t confirm or deny either way. Out of an abundance of caution, we’ve been proceeding with the assumption that they’re not real, but… it’s easy to forget, you know? There are intact books on the shelves that neither Tony nor myself have read before. I’ve now visited small towns on another continent that I hadn’t been to. Outer space seems accessible. Wong has told me about television episodes that I haven’t seen. I’ve been placed in a very convincing illusion before, but this is the best yet. It’s… If it is an illusion, then it’s staggeringly complete apart from the timeline discrepancies.”

A beat, then, “If it hadn’t been for those, I’m not sure if I’d have been suspicious at all. I can’t see the seams.”