Richard and Frances Myles are preparing for their annual European summer vacation in 1939 when they are visited at their Oxford college by old friend Peter Galt, who has a seemingly simple job for them. Galt asks if they would start their holiday in Paris, meet a man there, and then continue their journey as he directs. But in the heightened atmosphere of pre-war Europe, nobody is above suspicion, in fact the husband and wife are being carefully monitored by shadowy figures. Soon the couple are