Diane knew they might die here, all of them. The thought wasn't extraordinarily troubling to her, though she dreaded the pain and discomfort. One of the benefits of Fourthness (and they were all Fourths in this room, even, in his way, Isaac), was this muting of the anxiety about one's death. She had lived, after all, a very long time. She carried memories of the Spinless world, the vanished Earth as she had seen it as a child and on its last night: a house, a lawn, the sky. Back when she had believed in god, a god who made sense of the world by loving it.

The god she missed, perhaps even the god Dr. Dvali had been unconsciously invoking when he created Isaac. Oh, she had seen it all before, the fractured longing for redemption: she had lived with it, lived it. It had driven her brother Jason just as it had driven Diane. Jason's obsession had not been very different from Dvali's—the difference being that Jason, in the end, had offered himself on the altar, not a child.

Isaac's breathing began to deepen and his body cooled slightly. Diane wondered about his reaction to the ashfall. The link, of course, was through the Hypothetical machines, the half-living things that generated and inhabited and arose from the fallen dust. But what did that mean, what was the point of it, what was it meant to accomplish?

She must have spoken that last aloud—her mind was still a little muddled—because Sulean Moi said,

"Nothing, it's meant to accomplish nothing." Her voice was a raw croak. "That's the truth Dr. Dvali wants to deny. The Hypotheticals are comprised of a network of self-reproducing machines. That much we all more or less agree upon. But they aren't a mind, Diane. They can't talk to Isaac, not the way I'm talking to you."

"That's smug," Mrs. Rebka said from her corner of the darkness. "And not true. You talked to the dead boy, Esh, through Isaac. Wouldn't you call that communication?"

The Martian woman was silent. How strange it was to be having this conversation in the absolute darkness, Diane thought. And how Fourth of us. How would she have reacted to this predicament before her own treatment? Probably the fear would have overwhelmed her. Fear, and claustrophobia, and the steady awful sifting sound of ash (but it was so much more than ash) settling on the roof and stressing the building's beams and timbers.

"He told me he remembers Esh," Sulean said. "Memory is also an attribute of machines. A modern telephone has a larger memory than some mammals. I suspect the first Hypothetical machines were sent out into the universe for the purpose of gathering data, and I suspect they still do that, in infinitely subtler ways. Somehow, Esh's memory became available to the machines that killed him. He became a datum, which Isaac is able to access."