What happens in Edgar Allan Poe’s “The Fall of the House of Usher”?

In Edgar Allan Poe’s supernatural horror story "The Fall of the House of Usher," an unnamed narrator visits his childhood friend, Roderick Usher, at his decaying family mansion after receiving a letter detailing Roderick’s worsening mental illness.1

Roderick believes the house is sentient and exerts control over its inhabitants, who suffer from a "family evil." He also reveals that his twin sister, Madeline, is dying of a cataleptic disease. After Madeline supposedly dies, the men entomb her within the house. Roderick’s mental state subsequently deteriorates into madness.1

During a storm, the narrator reads a story to calm Roderick, but the sounds from the book seem to manifest within the house. Roderick reveals he has been hearing Madeline moving in her tomb, believing they buried her alive. Suddenly, the door bursts open to reveal a bloodied Madeline, who collapses onto her brother, killing him. The narrator flees as the mansion splits in two and collapses into the tarn, marking the end of both the physical house and the Usher bloodline.1