The story begins as the pestilence (the red death) this so called disease is killing people in the dominion.
In this scene the characters are dancing but stop dancing when the clock chimes, when the clock chimes it means someone is dying. The masks symbolize fear of death. The prospero believes he can escape death.
After being in these rooms there was no chance of trying to escape because the doors were sealed shut. As the clock is about to strike midnight an odd quest appears dressed as plague victim.
The Prince Prospero dies after trying to reach the odd figure. The people finally figure out that this odd figure is the red death.
All the guests realize that there is no one under the costume and they also die. The clock stops and the candles go out and the party is over at this point the red death has conquered on everythig.
The Prospero symbolizes mankind's inability to handle or accept death, The masks symbolize fear, and the Masquerade symbolizes illusion or escape from from reality.