Webster based The White Devil on newsletter versions of the story of the killing of Vittoria Accoramboni. Such recollections detailed how Vittoria, of a proud but poor family, married the nephew of Cardinal Motalto. In 1580, she met Paolo Giordano Orsini, Duke of Bracciano, previously married to Isabella Medici of the famous Medici family.
Upon meeting Vittoria, the Duke fell desperately in love with her and arranged for the Cardinal's nephew to be killed in order that he might secretly marry Vittoria. Pope Gregory soon found out and ordered Vittoria and the Duke to part and even resorted to having Vittoria imprisoned in the Castel Sant'Angelo under the suspicion of having killed her husband.
In 1585 a new pope was elected and amid the confusion of change Vittoria and Bracciano married and left Rome. In the play the Pope is misnamed Paul IV (he was Sixtus V, Paul IV having died in 1559). Eight months later the Duke died and the Medici family, wishing to protect their family interests, challenged his will, which placed Vittoria to be in charge of his fortune. When Vittoria refused to co-operate, the Medicis arranged for her to be killed. She was stabbed to death in Padua by Ludovico Orsini.