It's not all that often that the twins have reason to go off-campus, in the grand scheme of things; it's a large campus, with all the necessities of life available reasonably conveniently, and it's not as though they're familiar enough with the town to have a strong social attachment to it. Neither of them is fond enough of drinking for bars to appeal very much, and Edie finds movies as pointless as she does television.
Still, growing up in a boarding school makes a city this size something of a novelty, and the local natural history museum is high quality and worth the occasional visit. It's on the way back from one of these that Edie freezes as something alarming brushes against the edge of her range, and then turns to walk briskly in the direction of what feels an awful lot like a distressed mutant in need of help, bouncing the situation to Emily so that she'll follow.