In the begging of the story we are told that their is and pestilence in the air. That no one can cure.
The prince had gather all his friends, dancers,joksters etc.But he had put a clock in the room they were in and every time it charms they are reminded about reality.
When the clock stroked mid night and a strange figure dressed in an mask and has blood on him. He had made the prince very angry and then the prince charged him and the the masked man had killed him. and everyone is scared.And then everyone dies.
After the mask man kills the prince he then starts to kill all the people in the place .
Everyone one thought they could escape the red death they thought it was something g on the air but it was a person.