Holmes's brother, Mycroft, seeks his help in deciphering the story a man tells about being kidnapped and forced to translate for an injured Greek. Holmes investigates the disappearance of Paul Kratides, abducted by two villains, Latimer and Kemp, with the aim of forcing him to sign a document releasing his sister Sophie to marry Latimer.

Dr Trevelyan calls on Holmes on behalf of his friend Blessington, after a Russian father and son vanish during a consultation. Blessington knows of no one who wishes him ill, but he is found hanged the next day. Holmes investigates, with advice from Watson.