1861. When the body of an unknown woman is found in an Edinburgh close, Detective Constable Faro assumes the killing is a random act of violence - until he finds a playing card, the nine of diamonds, underneath her corpse. His superiors scoff at his suspicions of a serial killer, but days later a man is attacked in the street, and left badly bruised and battered with the nine of diamonds in his pocket. Faro believes there's a connection. Amongst all this, a servant at Faro's sweetheart Lizzie's goes missing. Could her disappearance be linked to the playing-card killer?