Antone Tojetti and his pretty daughter, Maria, are street musicians in Venice. John Strom, an American millionaire, makes love to Maria, and finally persuades her to leave for America with him. Her father sees them just as they are leaving, but she will not return to him. Two years later, Maria, abandoned by John, returns to her father, who has now become a guide in the mountains. She dies and Antone vows vengeance. Some time after this, John Strom, now married, is touring Europe and he and his party seek a guide to visit Vesuvius. Antone takes the position. John not recognizing in him the father of Maria. They make the ascent at night and when they have arrived at the top, Antone tells Strom that from another angle a better view can be had. When Antone and Strom have reached this point, Antone makes himself known, tells him what has happened to Maria and that he is going to push him into the crater. Strom is horrified, but Antone with the madness of a wild man, hurls him into the burning mass. His body in the descent falls in front of his wife and the remainder of the party, who are horror-stricken as they see his agonized face pleading with them from the mass below.