A painter working at the Louvre is struck by the Mona Lisa. When he meets a girl whom he believes bears a resemblance to the painting, and who wants him to become famous, he comes up with the idea of stealing the painting. Based on the real-life theft of 1911.

One autumn, Edgar, a 12 year old boy, spends a holiday with his mother at a plush hotel in Switzerland. His father, a busy lawyer, remains at the family home in Vienna. When he sees a stylish motorcar pull up at the hotel, Edgar wastes no time befriending its owner, an amiable dandy. The latter pays more attention to the boy’s mother than to the boy himself, and decides to use Edgar to wheedle his way into her affections. When Edgar realises he has been used, he is far from happy...