“I don’t know,” said Noxon. “Because we don’t know what Erectids can see. It seemed to me that while he saw Deborah most clearly, because she wasn’t slicing time at all, he also saw us, or never lost track of where we were. I think I need to tell myself to slice time much more deeply, and trust the cameras to record everything. Which means we need to arrive much earlier and place cameras. I’ll tell us to do that.”

“We should have done that in the first place,” said Wheaton bitterly.

“What happens to us then, after you leave that note. Do we just . . . disappear?”

“I don’t know,” said Noxon.

“You said Umbo did this all the time,” said Ram.

“Yes, but you see, I’ve always been the guy who gets the warning,” said Noxon. “When we change our behavior, does that eliminate the timestream of the selves that sent the warning? Or merely diverge from it, leaving them to live with the bitter consequences of the mistakes they warned us not to make?”

“You mean I might still be here, with my daughter dead?” asked Wheaton.

“I just don’t know,” said Noxon.

“Well, what if we find out that it’s so. Can we go back and give a different warning? Or appear to ourselves even before we got the note, and this time accept that yes, we’ll copy ourselves?”

“You don’t want to copy yourself,” said Noxon. “I know that.”

“You say that with absolute certainty,” said Wheaton, “but you’re the copy. You exist because of copying.”

“No,” said Noxon. “I’m the original. I’m the one who never murdered Ram Odin—a future version of him. I’m the one who got warned. Rigg was the one who had to live with the consequences of having done such a killing. He was the one who wasn’t saved.”

“None of us killed Deborah,” said Wheaton. “Unless you want to use some oblique causal chain that starts with ‘if I hadn’t insisted on seeing Homo erectus.’ But I tell you this: I don’t want to save my former self from seeing her dead, while I have to go on living in this world that doesn’t include her.”

“So you want to copy yourself?” asked Noxon.

“I don’t know what I want, except I want every version of myself to live in a world that includes a living Deborah!”

“There’s another choice,” said Ram. “We could leave Africa, go back to the States, and then go back in time and prevent the traffic accident that killed Deborah’s parents and blinded her.”