"'Personal interest," she said, cringing at how incriminating that sounded. "Really, it was part of his whole fascination with the post-Spin world—how people were adapting to it. And I think he was convinced the Martians knew more about the Hypotheticals than they included in their Archives, and maybe some of that knowledge had been passed around by Fourths along with the chemical and biological stuff."

"But the Genomic Security people didn't turn up anything either."

"No. They kept the file open for a while longer, or so they claimed, but in the end they didn't have any more luck than the PG had. The conclusion they obviously reached was that his research had gotten the better of him—that at some point he was offered the longevity treatment and took it."

"Okay, but that doesn't mean he had to disappear."

"People do, though. They take the treatment and assume a new identity. It means not so many awTkward questions when your peers start to die off and you still look like the picture in your grad book. The idea of starting a new life is attractive for a lot of people, especially if they're in some kind of personal or financial bind. But my father wasn't like that."

"People can carry around a fear of death and never let on, Lise. They just live with it. But if you show them a way out, who knows how they might behave?"

Or who they might leave behind. Lise was silent for a moment. Over the hum of the car's engine she heard a minor-key melody trilling from the high canopy of the forest, some bird she couldn't identify.

She said, "When I came back here I was prepared for that possibility. I'm far from convinced that he just walked out on us, but I'm not omniscient, I can't know for sure what was going on in his mind. If that's what happened, okay. I'll deal with it. I don't want revenge, and if he did take the treatment—if he's living somewhere under a new name—I can deal with that, too. I don't need to see him. I just need to know.

Or find somebody who does."

"Like the woman in the photograph. Sulean Moi."

"The woman you flew to Kubelick's Grave. Or like this Diane, who sent her to you."

"I don't know how much Diane can tell you. More than I can, anyhow. I made it a point not to ask questions. The Fourths I've met… they're easy to like, they don't strike me as sinister, and as far as I can tell they're not doing anything to put the rest of us in danger. Contrary to all that Genomic Security bullshit you hear on the news, they're just people."

"People who know how to keep secrets."

"I'll grant you that," Turk said.

* * * * *