Patrick Mahon is arrested on suspicion of murder after showing up at the Waterloo train station in London to claim his bag. He quickly confessed that the bloody knife and case inside were connected to the death of his mistress, Emily Kaye. Mahon then directed the Scotland Yard detectives to a particularly grisly scene in a Sussex bungalow, where they found Kaye's remains, dismembered and hidden among hatboxes, trunks, and biscuit tins.
Mahon's suspicious wife set off the investigation by asking a friend and former police officer to check out the baggage claim ticket that she had found in Mahon's suit earlier. Following his arrest at the train station, Mahon claimed that Kaye, who was pregnant with his child, had slipped and struck her head, thus causing her death. He argued that he was only trying to protect his marriage by disposing of the body in the manner in which he did.
The medical examiner in charge, Sir Bernard Spilsbury, had no choice but to attempt to reassemble Kaye's body in order to find the cause of death. Over the course of several days, he painstakingly pieced her body back together from the remaining assorted parts. Missing only her head, Spilsbury was able to discount Mahon's claim that a single fall was responsible for her death. He also deduced that Kaye had been carved up with a knife that Mahon had purchased prior to the murder.
An important investigation innovation came about from the crime scene at the Sussex bungalow: The officers, who were not outfitted with gloves, were forced to pick up Kaye's remains with their bare hands. After the Mahon investigation, rubber gloves became standard equipment at murder scenes.
Much of Mahon's case is bound up in myth and legend. Purportedly, Mahon told a fellow inmate that he was burning Kaye's head on the stove when her eyes suddenly popped open.
Mahon was executed for murder in September 1924.