London, 1852. On the shocking discovery of a passenger's body on the Great Western Railway excursion train, Detective Inspector Robert Colbeck and his assistant, Sergeant Victor Leeming, are dispatched to the scene. Faced with what initially appears to be a motiveless murder, Colbeck is intrigued by the murder weapon - a noose. When it emerges that the victim had worked as a public executioner, Colbeck realises that this must be intrinsically linked to the killer's choice of weapon. However, the further he delves into the case, the more mysterious it becomes. When a second man is strangled with a noose on the train, Colbeck knows that he must act quickly; can he catch the murderer before more lives are lost?