A woman is burned to death with strange markings which is same thing with a previous victim. They investigate and they think their perp is man obsessed with fire. However he is at his apartment when a third attack happens. They reexamine their victims and find that they all related to a woman who was a friend of the second victim. They manage to stop her before setting a blaze to a fourth victim. Also in this episode Cyril is found to have a job as teacher and David tries to overcome his insomnia.