“We could solve the problem from here, but obviously we’d end up stuck in this timeline if we did. Now, for Cam’s lot, that’s no big deal, because they fully intend to fuck off back to the stars when we’re done, and it doesn’t affect them much which universe they’re in. But for the rest of us, we’d have a choice between living in a trilobite’s gut for the rest of our natural lives or suffocating PDQ outside. So, yes, we’re working this to let us all get home in the end, those that want to.” She glanced at Ertil, and Alison guessed that the rodent would be after some kind of diplomatic asylum, most probably with the Cousins and Dr. Rat’s extended family.

“What about creatures—people—who’ve already crossed over?” Julian asked. “We took in a load of rat-creatures, for example.”

“We don’t have time for diplomatic treaties and repatriation, Jules. We’ll have to live with it.”

“What about the rats, though?” This from Mal. “You’ve seen how they live, en masse. They’re going to be stuck, aren’t they?”

Kay blinked. “I don’t think you…We’re trying to stop the universe collapsing. We can’t pause along the way to effect fucking societal change in a non-human culture we know very little about. Priorities, love.”

Mal looked mutinous but subsided.

Kay peered out over her audience, a lecturer whose students were probably not going to pass the end-of-year exam. “The problem is that everything we know is being actively maintained by this…Ediacaran sponge-monster thing. And it’s finally wearing out. When enough of it dies off—which is going to be really soon, because we cut it very fine indeed—it can’t keep the lights on. And then that’s all she wrote, okay?” Dumbed down enough for you? said her expression, but it wasn’t patronizing if people really did need the CliffNotes version to understand it.

“But,” Kay went on, grinning like a madwoman, “I have a fucking library of equations right now that show that if you balance the field just so, then it should stand up on its own. You can whip away the tablecloth and all the plates stay put. At which point every timeline just continues on its own, theoretically indefinitely. Job done.” She made it sound simple, but Alison was looking inwards, where the Posticthyan computer was throwing up complex rotating models demonstrating the forces and principles involved. The models were doubtless hopeless simplifications, and even then Alison had difficulty understanding them. But the main thing Kay wasn’t saying was how delicate the operation was, how exact any tinkering would have to be.

“How is this to be accomplished, precisely?” Rove broke in. “You’re talking blithely about playing with universal forces.”