Monte Verita was once the site of a famous avant-garde community attracting celebrities such as Isadora Duncan, Carl Jung and Thomas Mann. Legend has it that its leader had himself sealed in a grotto in the hillside; when it was unsealed, he had vanished. It is now 1938, and nearby Ascona is hosting a conference on the locked room mystery. A number of the participants are secretly agents for the Great Powers, jockeying for position on the eve of World War II. One of them accepts a challenge to be sealed in the same grotto and escape, but before he can do so, he is himself the victim of a...