Outer Dark is a story of sin and retribution, played out in folktale fashion against an indefinite time and place. It begins with the birth of a child, the incestuous offspring of Culla Holme and his sister Rinthy, who live in the mountainous recesses of Johnson County (no state is indicated). Culla, ashamed and frightened by his misdeed, refuses to summon aid for his sister, forcing her to give birth in the secrecy of their isolated cabin. When the child, a boy, is finally born after a long laboring, Culla takes the baby deep into the surrounding woods and leaves it, later telling Rinthy that it was sickly and died while she slept. Rinthy, however, refuses to believe her brother, especially when, after being led to the supposed grave site, she can find no trace of the baby’s remains. Convinced that Culla has given the child to a wandering tinker, who appeared at the cabin shortly before the birth, Rinthy sneaks away from her brother in a blind search for the old man and her baby. When Culla discovers her absence, he follows after her, with no real understanding of his purpose in doing so.
The novel is thus constructed in terms of the encounters these two characters experience as they wander throughout a dreamlike and most often nightmarish landscape. The tinker disappears, known only by rumor, but Rinthy is led by a kind of innocence and faith that protects and sustains her. Culla, on the other hand, following in his sister’s steps, becomes an Ishmael in this outside world, suspect and fugitive wherever he goes. His guilt concerning the child dogs him and takes on a universal identity. He is anathema to those he meets.
At intervals during Culla’s wanderings there appear three dark figures—perhaps escaped murderers, perhaps malignant supernatural beings, perhaps even the demoniac shapes of Satan himself. Dressed in clothes stolen from the grave, these manifestations plague the land with atrocities, deeds for which Culla is inevitably blamed. The leader, clad in black, proclaims himself a minister. His two followers are a psychopath named Harmon (the only one of the three with a name) and a mute, monstrous idiot. Emblems of horrifying evil, these three are also figures of judgment and retribution who face Culla with his overwhelming guilt and exact punishment in a final scene of inevitable justice.