It's 2193, almost a century since scientists on Callisto discovered immortality. Every year, the Party sends a group of Earth's best and brightest to receive this immortality. No one ever comes back.

Four people are making the journey to Callisto to receive immortality. Padraig, a brilliant physicist, dying of cancer. Cassandra, an orphan from the irradiated ruins of New York. Jocasta, a veteran of the Yugoslav Wars. Gautier, whose presence on Callisto no one will adequately explain. Immortality is meant to change them for the better. But once they're on Callisto, what happens when they just want to go home?