St. Elmo and Murray Hammond, his cousin and best friend, are both in love with a young woman named Agnes Hunt. Although Agnes loves Murray, she rejects him for being too poor. Instead, she accepts the wealthy St. Elmo's marriage proposal. St. Elmo's mother holds a ball to celebrate the engagement. After the betrothal is publicly announced, Murray and Agnes meet covertly in the gardens. St. Elmo discovers their affair, challenges Murray to a duel, and kills his cousin with the first shot. The Devil possesses St. Elmo, and he becomes a cruel wanderer, spreading misery and misfortune where he travels.