Due to an experimental vaccine, Dr. Robert Neville is the only human survivor of an apocalyptic war waged with biological weapons. Besides him, only a few hundred deformed, nocturnal people remain - sensitive to light, and homicidally psychotic.
A knight in the service of a duke goes to a coastal village where an earlier attempt to build a defensive castle has failed. He begins to rebuild the duke's authority in the face of the barbarians at the border and is making progress until he falls in love with one of the local women.