Exposition: The Red Death is a deadly disease that has wiped out most of the population of Prince Prospero's domain. He has brought his closest friends to live in his massive palace to live with him and escape the Red Death.
Climax: Prince Prospero and his friends have been living in his palace for six months and he decides to throw a masquerade. They're all enjoying the party when a masked figure dressed as the Red Death walks in and draws everyones attention. Prospero chases the Red Death down seven rooms and the Red Death kills him when he gets to the seventh room.
Resolution: Everyone eventually dies from the Red Death and the moral of the story is that you can't escape death and that you should take care of the less fortunate, be giving.