England, 1935: Professor Henry Barstow, an atomic physicist on vacation in Cornwall, settles into his hotel, has lunch, and chats with a white-haired gentleman in the hotel bar after the meal. Just a few hours later, a man enters the hotel who looks strikingly like the absent-minded Professor Barstow and registers under the name Conway Carruthers. Barstow's car is soon found as a burned-out wreck in the moor, and he is reported missing. But who is this Carruthers, who travels all the way to Bucharest to save humanity from the threat of nuclear weapons?.