In an apparent idyll high in the Swiss Alps, a secluded village society prepares for the next wedding. Amina is to be the lucky one this time. The groom Elvino, however, soon turns his attention back to his former wife because Amina sleepwalks into the bed of a stranger who has just arrived. Count Rodolfo, son of the former lord of the manor and travelling incognito, cannot convince the villagers of his innocence nor that of Amina, until she sleepwalks again and the collective belief in the supernatural is put to the test.