Noxon shook his head. “How can I slow myself down enough to sense something whose existence in our timeflow has no duration?”

Ram shrugged. “Got any better ideas?”

“The ship has been calculating,” said the expendable, “and your physics is correct. Each instant of the backward path would have no duration. Except that this is also true of forward paths, and you see those.”

“Because of causal continuity,” said Noxon.

“That’s your guess,” said the expendable. “It’s a good guess, unless it’s wrong. But I think you’re probably right. That doesn’t change anything. The other timeflow also has causal continuity. So what’s to say there isn’t a lingering image? Not an after-image, as with ordinary timeflow, but a pre-image, a semi-physical memory of what is about to happen, because in that timeflow, it already happened. Each instant caused the next and the next. Maybe there’s enough of causality clinging to each instant of a human life that it becomes visible.”

“If that were true,” said Noxon, “I should see them already.”

“No,” said the expendable. “Because they’re unhappening. Causality is unraveling, in the direction we’re going. Each instant is unmade as you sense it. So instead of a path, a continuity of events, it’s a series of discontinuities. An unpath.”

“Clever naming,” said Noxon. “But you don’t know what you’re talking about.”

“On the contrary,” said the expendable. “I don’t know what you’re talking about, because I’ve never sensed these paths. But when we’re talking about the logic of causality and time, my guess is no worse than yours. And even if I’m wrong, my wrong guess will be more precise than yours.”

Ram barked a laugh. “See what I put up with for all those years in space?”

“See what I put up with, day after day in the forest,” said Noxon.

“I don’t expect you to understand what I put up with,” said the expendable.

“We’re in a box,” said a mouse. “That’s something to put up with.”

“If he’s right about this,” said Ram, “and it’s not as if I know anything here, but if he’s right, then at least you’d know where to look for these not-quite-instantaneous instants of my outbound path. My life was pretty much limited to sitting in that chair. Or lying on that bed. Or exercising in there. I swivelled the chair a lot. Not like a little kid spinning around, but from station to station. To do different jobs. I don’t know what you need—motion or stillness. That chair is where I sat still most of the time. Or if you need me walking, I only followed certain paths, but I did them over and over.”

“Do you think I haven’t been looking for anything anomalous since I got on this ship?”