The two noble families, Rossitz and Warwand, are related, and since the succession of both lines has been settled by a decree stating that if one family dies out the combined property shall go to the surviving family, they keep close, suspicious and resentful watch upon each other. The two families are obsessed by suspicion and a deep desire for revenge. Ottokar and Agnes are children, but from different families, and they are in love. They manage to exchange costumes and each is killed by its own father in mistake of the other. When they are lying bathed in their own blood the elders finally comprehend the insanity of the delusions.