American detective Grant Colwyn is spending his holiday in England when it is brought to his attention the strange behavior of a fellow guest. A well known doctor, Sir Henry Durwood, claims that the young man is suffering from a rare form of epilepsy and may soon present a danger to other hotel guests. The strange young man leaves hotel the next day and finds a lodgings in a nearby inn, but soon after that a murder is committed in a neighboring town, and the same young man is the only suspect. Although all the evidence points to him as the murderer, Grant Colwyn believes in his innocence and sets out to prove it.
