A disease known as the Red Death plagues the unnamed fictional country where this tale is set.  The disease causes its victims to die quickly and gruesomely; every person who contracts this deadly disease is overcome by “sharp pains,” “sudden dizziness,” and “profuse bleeding at the pores,” and dies within half an hour of contracting the virus. However, Prince Prospero feels happy and hopeful despite the disease spreading rampantly through his country because he believes that he has the wealth and power to avoid contamination. He decides to gather 1,000 of the knights and dames in his court into his palace and lock the gates and weld them shut in order to fend off the plague. Prince Prospero and his companions ignore the illness ravaging the land and leave Prospero’s subjects to fend for themselves. Prince Prospero fills his palace with plenty of wine and provisions. He also brings in means of entertainment: buffoons, improvisatori, ballet-dancers, and musicians. With locked doors, food, drink, and means of merriment, Prince Prospero is convinced that he and his companions can securely wait out the Red Death. 

After several successful months avoiding contamination, Prospero throws a lavish masquerade ball. For this celebration, he decorates the rooms of his eccentric house in single colors. The easternmost room is decorated in blue complete with blue stained-glass windows. The next room is purple with purple stained-glass windows. The rooms continue westward, according to this design, in the following color arrangement: green, orange, white, and violet. The seventh room is black but with red windows instead of the monochrome design featured in the other rooms. Also in this room stands an ebony clock. When the clock rings each hour, its sound is so loud and distracting that everyone stops talking and the orchestra stops playing. When the clock is not sounding, though, the rooms are so beautiful and strange that they seem to be filled with dreams swirling among the revelers. Most guests, however, avoid the final black room because it contains both the unnerving clock and an ominous ambience created by the dark fabrics and red windows.

The clock in the black and red room rings an unsettling twelve times to indicate that it is midnight and, almost instantly, a new guest appears in the palace, something that should have been impossible given that the inhabitants welded the gates shut. The new guest is also dressed for a masquerade ball but he appears more ghoulish and more sinister than the rest of the partygoers. The newcomer’s garments resemble a funeral shroud and his mask looks like the face of a corpse. The mysterious guest’s mask is the most unsettling aspect of his appearance because his face reveals spots of blood suggesting that he is a victim of the Red Death. Prospero interprets the figure’s appearance as an insult and becomes angry that someone with so little humor and levity would join his party. Prospero calls on his guests to seize the masked figure because he is unwelcome. However, the other guests are so afraid of this unexpected arrival that they refuse to go near him. Unchecked, the mysterious guest proceeds to walk through each room beginning in the blue room. Prospero finally catches up to the mysterious guest in the black room and drops dead the moment he is in his presence. When other party-goers enter the room to attack the cloaked man for killing their prince, they find that there is nobody beneath the costume. Everyone then dies, for the Red Death has infiltrated the castle. “Darkness and Decay and the Red Death” have at last triumphed.