Aubrey, a young Englishman, meets Lord Ruthven, a man of mysterious origins who has entered London society. Aubrey accompanies Ruthven to Rome, but leaves him after Ruthven seduces the daughter of a mutual acquaintance. Aubrey travels to Greece where he becomes attracted to Ianthe, an innkeeper's daughter. Ianthe tells Aubrey about the legends of the vampire. Ruthven arrives at the scene and shortly thereafter Ianthe is killed by a vampire. Aubrey does not connect Ruthven with the murder and rejoins him in his travels. The pair are attacked by bandits and Ruthven is mortally wounded. Before he dies, Ruthven makes Aubrey swear an oath that he will not mention his death or anything else he knows about Ruthven for a year and a day. Looking back, Aubrey realizes that everyone who Ruthven met ended up suffering.
Aubrey returns to London and is amazed when Ruthven appears shortly thereafter, alive and well. Ruthven reminds Aubrey of his oath to keep his death a secret. Ruthven then begins to seduce Aubrey's sister while Aubrey, helpless to protect his sister, has a nervous breakdown. Ruthven and Aubrey's sister are engaged to marry on the day the oath ends. Just before he dies, Aubrey writes a letter to his sister revealing Ruthven's history, but it does not arrive in time. Ruthven marries Aubrey's sister, kills her on their wedding night, and escapes.
Italiano
Nel Maggio del 1816, ricordato come "l'anno senza estate", Lord Byron, accompagnato dal medico Polidori, invitò a Villa Diodati Percy Bysshe Shelley, la sua compagna nonché futura moglie Mary Wollstonecraft Godwin e Jane Clairmont, sorellastra di Mary e all'epoca amante di Byron. A causa della pioggia incessante passano il tempo leggendo storie di fantasmi, come le Fantasmagoriana o il romanzo Vathek di William Beckford, finché Byron propone di fare una gara a chi riuscirà a scrivere il racconto di paura più bello. Soltanto due riescono a portare a termine la sfida: Mary scriverà il suo celebre romanzo Frankenstein e Polidori, partendo da un frammento di una storia di Byron, porterà a termine Il Vampiro. Ma anche Byron e Percy Bysshe Shelley riuscirono a scrivere i loro racconti, meno importanti.