Plot
A writer named Adrian Messenger believes a series of apparently unrelated "accidental" deaths are actually linked murders. He asks his friend Anthony Gethryn, recently retired from MI5, to help clear up the mystery, and provides him with a list of the victims' names. Soon afterward, Messenger's plane is bombed while he is en route to collect evidence to confirm his suspicions and, with his dying breath, he tells a fellow passenger the key to the mystery.
The passenger survives and turns out to be Raoul Le Borg, Gethryn's old World War II counterpart in the French Resistance. The two of them join forces to investigate Messenger's list of names and decode his cryptic final words. They are joined by Lady Jocelyn Bruttenholm, Messenger’s cousin and a former love interest of Gethryn, who Raoul is strongly attracted to.
The first conclusion Gethryn and Le Borg draw from Messenger’s words is that there is important information in the manuscript of his unpublished book. Unfortunately, the murderer has beaten them there; he has taken several pages and re-typed them, removing certain information, and murdered the typist to conceal the error (encountering Jocelyn on his way out). After inspecting the manuscript, Gethryn spots the error, but he is powerless to undo it, and arrives too late to save the typist. From Jocelyn’s brief encounter with the murderer, Gethryn determines that he wears realistic masks to disguise his appearance.
Next, Gethryn and Le Borg visit the only living name on the list, James Slattery. When they arrive, they are told by James' invalid twin brother, Joe Slattery, that James died of a heart attack several years earlier. The two of them leave in disappointment, assuming all names on the list have died. That night, however, Joe sees and recognizes the masked murderer, who pursues him, knocks him out and pushes him into the ocean with his wheelchair, drowning him. The following day, his mother reveals the truth to Gethryn; “Joe” was actually James, who impersonated his deceased brother to collect his disability pension.
From James' mother, and from the widow of another name of the list, Gethryn and Le Borg establish that all on the list were together in a prisoner-of-war camp camp in Burma, where a Canadian sergeant betrayed his fellow prisoners, foiling their escape attempt. It stands to reason that the Canadian is the murderer, and killed each of the names on the list to prevent them from identifying him. They deduce that he is about to come into prominence and cannot risk being recognized. Almost by accident, Messenger’s final clue falls into place; it is revealed that the Canadian stands in line to an inheritance of the Bruttenholms (pronounced "Brooms"), Jocelyn’s family of landed gentry, who avidly engage in fox hunting.
Having disposed of all possible witnesses to his wartime treachery, the Canadian, George Brougham (pronounced 'Broom'), appears at a Bruttenholm estate fox hunt and introduces himself as a member of the family (he has previously been seen only in disguise). It then becomes clear to the visiting Gethryn and Le Borg that Brougham's next victim is to be the young heir, Derek, who comes before Brougham in inheritance. In an attempt to divert Brougham, Gethryn informs him of his investigation of Messenger’s list, calculating to set himself up as the next victim.
That night, Brougham sabotages the next morning’s hunt by laying a drag with a fox in a sack over the fields. He especially marks a blind spot behind a high wall, and moves a large hay tedder behind, intending for Gethryn (who has been given the honor of leading the hunt) to be impaled upon its lethal tines. Unbeknownst to Brougham, his plan goes awry when a farmer repositions the tedder early the next morning. The hunt begins, but comes to a halt at the specified spot. Gethryn reveals to the gathered crowd that he discovered and removed the hay-tedder booby trap earlier that morning and, with the help of the lead fox hound, will detect the scent of the culprit amongst a group of hunt saboteurs. Brougham, once again disguised, is identified and runs off, mounting Derek's horse. When Derek shouts a command to the horse, the animal stops short, throwing Brougham and impaling him on the very same machine he intended for Gethryn.
