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.