Aristide Valentin, Paris chief of police, has decided to stage a grand dinner party at his estate. The estate has only one entrance with a garden is protected by a high wall; there is no entering or leaving, except by the main entrance which is guarded by Valentin's steadfast servant, Ivan. However, a murder most foul, a decapitation occurs, and it will be up to Father Brown to use all his wits to solve this heinous murder.