Two newcomers arrive on the social scene of London's noble classes. The first one is Lord Ruthven. He is frighteningly pale and has a self-absorbed, uninterested attitude. Yet everyone he meets is attracted to him and seeks to win his affection. The other man is Aubrey, a handsome, wealthy orphan who uses his wild imagination more than his judgment. Aubrey becomes fascinated by Ruthven and obtains approval to accompany the lord on his travels through Europe.
When they tour in Rome, Lord Ruthven gambles and give his money to impoverished people with vices, rather than virtuous people in need. He also tries to seduce a young, innocent woman, though Aubrey tries to stop him. Appalled, Aubrey leaves Ruthven and travels to Athens, where he meets Ianthe, a beautiful Greek girl. He falls in love with her, and she tells him supernatural tales, including the legend of the vampire.
One day, Aubrey goes on a trip. Ianthe and her family urge him to return before nightfall because his route goes through the woods haunted by vampires. But Aubrey runs late and he is caught in a storm in the woods at night. He hears a scream and eventually finds the dead body of Ianthe. She has blood on her breast and neck and bitemarks on her throat. The townspeople who see her corpse believe that her death was the doing of a vampire. Back in Athens, Aubrey contracts a violent fever. In his delirium, he calls out to Ianthe and Ruthven and pleads for the latter to spare the former.
Ruthven appears by Aubrey's bedside and attends to him. When Aubrey recovers he proposes traveling with Ruthven to take his mind off Ianthe. On their journey robbers attack them and Ruthven is mortally wounded. On his deathbed, Ruthven demands that Aubrey make an oath with him: that he will not mention his death for a year and a day.
When Aubrey returns to London, he meets the surprisingly healed Ruthven, who starts seducing Aubrey’s sister. Aubrey tries to warn his sister and their guardians. But everyone dismisses him as crazy and Aubrey can't reveal much, due to the oath he pledged to Ruthven. Ruthven and Miss Aubrey marry the night before the oath expires. Aubrey's condition worsens and he dies. Miss Aubrey is also found dead, the presumed victim of a vampire.
