A young German prince of Protestant faith becomes embroiled in a diabolical net of political intrigue and religious conspiracy. During his stay with the prince in Venice, the Count von O*** witnesses how the fragile and impressionable character of his young companion falls victim to the insidious machinations of his enemies whose aim it is to get him to convert to Catholicism and then to overthrow the Protestant rulers of his princedom. His faith is challenged by supernatural apparitions and his moral steadfastness is subverted by the lure of gambling and tragic love affairs. Fate takes its course and steers mercilessly towards a calamitous climax of violence and death.