During boyhood, Samuel and his twin brother, Morgan, invent and in a sense inhabit a world and language called 'Nahum'. Years later – after a family tragedy and long separation – Morgan is a celebrated novelist, while Samuel makes a living translating his brother's fiction from Nahum into English.

The greater part of Dying in the First Person's force is figured in its language. It begins with Samuel's effort to imagine the recovery of Morgan's drowned body from a river in the Netherlands, where he has lived with a woman called Ana for some years. Ana accompanies the body home, and brings a secret or two with her.