The forces of darkness are gathering and Rachel and Gareth are oblivious, until a sequence of strange happenings alerts them of a plot to kill Galahad and his men. They go back in time to warn Merlin and Galahad, and unknowingly trigger off a succession of dreadful events. The evil sorceress s Morgause and Rathyen are seeking revenge and have enlisted help from the most malevolent quarters. The twin s mission will be fraught with daring rescues and danger. The Battle of the Underworld will soon be upon them, but can they defeat an undead army from Hades, sent by the darkest master of all?