Phyllis Clavering, the girlfriend of Captain Drummond, is kidnapped. Murderer Mikhail Valdin and his sister, Irena Soldanis, seek revenge for the death of her husband, sent to the gallows a year ago through Drummond's actions. Though Valdin could shoot Drummond, he informs the captain that it would be too quick. Drummond and his friend Colonel Nielsen are instead given a series of riddles to solve.