B, captain of the first crewed mission to the Silver Planet, does not think of the planet's native race as people. Silvers may look human, but their emotional spectrum is severely limited. B allows his team to capture, study, and even kill the creatures.

When B bonds with a Silver called Imms, everything changes. B's not sure if Imms's feelings are genuine or imitation, but B's growing friendship with Imms becomes his anchor in a strange world. Following a shipboard fire that kills most of B's team, B takes Imms back to Earth. He sanitizes the story of the fire—for which Imms bears some responsibility—so that Imms is recast as its hero rather than its cause.

Life on Earth threatens the fragile connection between the two men. As Imms seeks independence from a bureaucracy that treats him like a test subject, he begins to experience the gamut of emotions—including a love B is frightened to return. And as B and Imms's story about the fire threatens to unravel, Imms must use all he's learned about being human to protect B.