Guido Capanelli is an adventurer, his good looks and courtly bearing helping him through many successes. He has gained entrance to the best society, incidentally making the acquaintance of Princess Dione, whose father. Prince Paul Ragosin, is in feeble health. Prince Ragosin has expressed a wish that Princess Dione shall marry Feodor Strogoff, and on his death bed gains the promise from Dione that his wish shall be gratified. Feodor allows Guido Capanelli to be Dione's greatest source of sympathy in the hours of her grief, and in consequence, Guido so ingratiates himself with the Princess that she marries the adventurer, regardless of her pledge. Previous to Prince Ragosin's death Dione became interested in Katerina Vlasoff, a girl who is a street vendor of crude images and daughter of Peter Vlasoff, a drunken beast. When the girl returns home one evening without having made a sale all day Vlasoff sends her into the streets, threatening her with harm if she does not return with money to buy him wine. Katerina is accosted by Guido Capanelli, and; submits to his advances that she may have money to take home. She is so humiliated that she is glad to take her brother's advice to visit Princess Dione, the friend of everybody who is poor and in distress. Touched by Katerina's story, Princess Dione sends the girl to a convent, having gained Prince Paul Ragosin's consent to thus befriend the outcast. After Dione and Guido are married, Katerina returns from, the convent to make her home with her benefactress. Guido, under threat of exposing Katerina, demands a renewal of their relations and the deceitful couple start at once to plot against Princess Dione. When the Princess falls ill, they appoint themselves her nurses and in neglecting to administer medicines properly create a comatose condition that closely resembles death. The Princess is buried and Guido and Katerina establish themselves in control of her lands and fortune. When Dione had married Guido she received a book from Feodor Strogoff with an inscription in effect that he would always stand ready to befriend the woman he loved, but had discarded Slim for another. After the Princess is entombed, Feodor visits the sepulcher and discovers that Dione is alive, having simply been in a trance. Convinced, by what she herself witnessed of the treachery of her husband and Katerina, the Princess goes with Feodor to Rome, for the purpose of biding their time for vengeance. Guido and Katerina visit Rome and Guido becomes enamored of a famous beauty who has become the toast of the town. The woman is slow to accept Guido's advances, but finally tells him that a famous ring that has been buried with the Princess Dione will be the price of her affection. When Guido returns to the sepulcher to rob his wife's corpse, he finds the coffin empty. As he turns away from the tomb, he sees what he believes to be the ghost of the Princess. The apparition drives him insane and he runs to a nearby cliff and throws himself into the ocean. Katerina returns to the street from whence she came and Princess Dione and Feodor find happiness in marriage.