In 1913, Sherlock Holmes, virtually in retirement, is persuaded by Inspector Alec MacDonald of Scotland Yard to take on a baffling case. Three dead bodies have been found in London’s East End, all with no discernible cause of death, but the expressions on their faces suggest that they all died in a state of terror.
Holmes, accompanied by Dr Watson, begins an investigation, but before he can make any real progress he is visited by the British Home Secretary and a German Diplomat, Count Udo von Felseck, who tell Holmes that a German envoy, on a secret mission to Britain, has disappeared from Felseck’s house in Buckinghamshire. Unless Holmes can track him down, war between the two countries will become inevitable. Holmes considers the possibility that the two matters are related and that someone is not telling him the truth.