Detective Murdoch investigates the murder of well-known Toronto lawyer Percy Pollack. The body is delivered in a trunk to Toronto Police Station No. 4 with an ominous note addressed to Inspector Thomas Brackenreid, who believes he may be the next victim. While the Inspector uses the more traditional police techniques, Murdoch takes a more scientific approach in solving the crime particularly in determining the time of death, which proves crucial to solving the murder. Meanwhile, Murdoch catches the eye of the Chief Constable who suggests to him that he may be the ideal candidate for the vacant Inspector position at Station No. 3.