John Gielgud charmingly portrays the novelist-cum-officer dragooned by the British spy service into travelling to Switzerland on the trail of a Nazi spy. He is assigned two assistants - a rather naive, but keen, Madeleine Carroll "Elsa" and a suitable sleazy, but lethal, Peter Lorre "as The General". Their first attempt to fulfil their mission goes awry somewhat, as they dispatch the wrong person....