Part I: His family having moved following their ordeal at Michael Hawkins' hands Creegan is deemed fit to return to work but both he and Susan are resentful of bright new colleague Martin Simmons,brought in to replace the slaughtered Rivers. A charred corpse is discovered in a disused mental home,bearing the mark Y Me. A second murder occurs committed in the same way and again Y Me is the motive. The victim was last seen in the company of her boyfriend Andy,according to her baby-sitter Lynn Southy and he becomes the prime suspect. Part II: Susan interviews a noted arsonist imprisoned in France,Jacques Dutronc,on the psychology of arson whilst both Andy and another fire-raiser,former asylum inmate Miles Van Der Twemp are cleared as having no links to both murders. A new suspect enters the frame, Susan Etchells,who was in the asylum under her mother's name,Susan Winters - the latest victim being a teacher who sacked a woman by that name. Creegan finds that he has to go back to school,literally,to discover the disturbed woman behind the attacks and risk his life to save another victim.