The forensic psychiatric Sally Rowe is called by Detective Martin Mackenzie to analyze the profile of the teenager Alex Forbes, who was found in a train station holding the body of his schoolmate Nigel Colby and with powder in his hand. Alex discloses his relationship with Nigel, who believes that they were descendants of the Templar Knights, and how Nigel used the power of his mind to control him. Mackenzie believes that Alex is the killer, but Susan investigates the family of Nigel under pressure of Alex's father, and finds that all of them belong to an ancient and powerful secret society.