With Conan of Cimmeria, Red Sonja. the deadly warrior-maid battles the dark sorceries of the prison Isle of Os Harku, where a dark force feeds on the evil in the hearts of the traitors, murders and thieves incarcerated there. It captures Athu, a SHemite sorcerer and drives him to attempt an escape and then search for the entrance to Hell. During a sorcerous storm, the prisoners escape on a stolen ship. But also on board is Red Sonja.