Prospero gathers 1,000 of his aristocratic friends, seeking out those who are healthy ("hale") and optimistic and fun loving ("light-hearted") and seals them in an abbey to escape the red death, which is ravaging his kingdom.
The abbey is secluded and surrounded by strong, high walls, and the Prince and his guests secure the structure against intruders by welding the gates shut. The welding also insures that no one can leave. Here, Prospero, ironically described as "dauntless" and "sagacious," plans to ride out the red death with his friends. Others might suffer: they believe they will not.
The red death, like the Bubonic Plague or black death, is described as a disease that kills quickly and horribly. For about five or six months, however, Prospero and his friends live safely while the pestilence rages outside their walls.
Yet the illusion of safety ends. The point of the story is that it is impossible to wall death out. The narrator suggests that some might have considered Prospero "mad," and even amid the revelry and gay pleasures of the masque the guests experience unease. This unease is not without basis, for death invades the revels in the form a mysterious stranger, who comes dressed as the red death and kills them all.