Tuck is on his last legs, literally. He's the last functioning bot in the galaxy, a broken machine that used to look like a man. Long ago, bots were a luxury on Earth, back before they were hunted down and destroyed. Now he wanders between planets, searching for spare parts that can keep him running for a few more years. But he's out of parts, and he's nearly out of time. He was originally programmed to value human life, even if they don't value his, but he can't ignore his own need to survive, at any cost. The truth is, Tuck is afraid to die. That's why he's haunted by memories of the sixteen people he has killed over the last 150 years. After a particularly dangerous run-in with a collector, Tuck meets a mysterious man dressed in white who offers a solution. In exchange for some help in a less-than-legal business venture, he'll give Tuck what he really wants: immortality. Tuck knows it's a bad idea, but he can't ignore it. Even if it means killing again.