As a bustling crowd clambers aboard the Great Western Railway excursion train raking them to an illegal prizefight, the guard fears for the safety of his rolling stock. Little does he expect, however, the murder of one of his passengers, public executioner Jake Bransby. Detective Inspector Robert Colbeck and his assistant Sergeant Victor Leeming are sent to the scene and are intrigued by the murder weapon--a noose. When a second man is strangled by a noose on a train, Colbeck must act quickly to catch the murderer before more lives are lost.