A beautiful girl and a Russian professor combine to make the Saint's holiday in Switzerland one of the most memorable of his career. Someone is out to return the scientist to his homeland until the Saint intervenes.
Simon interrupts an armed robbery and is told by Teal that the gang in question are are building up to a last big job.
Persuaded to follow a defecting civil servant who has been tricked into smuggling secret papers into East Germany, Simon finds himself playing the part of a British agent to save the man's life.
A double-agent, codenamed Merlin, steals a new sleep gas and tries it out on Steed. Awaking 24 hours later, with Merlin his prisoner, Steed can't turn him in... as if everyone has vanished.
