A mysterious death horrifies the residents of a small Irish village. Where the police are powerless, two young detectives take on the case - Derval O'Ryan and Walter Murphy. The investigation soon pits them against the "temporaries", former IRA fighters; A Hungarian student named Negyesi was also inexplicably involved in the events. Finally, it turns out that the roots of the terrible crime stretch back centuries; brave heroes, neglecting mortal danger, decide to fight with the ancient Evil who lives in a gloomy, abandoned mansion...