Prince Prospero’s response to the plague is to have a big party for the wealthy in his kingdom, locking the poor suffering subjects out.
In order to distract them from the death and suffering outside their walls, the prince provides his guests with "all the appliances of pleasure,’’ and holds a masquerade ball after the fifth or sixth month. (enotes characters, third link)
The prince is “happy and dauntless and sagacious” (enotes pdf p. 4). He does not care what is going on in the kingdom. He is not sick, and as long as he can lock himself into his luxurious palace, his "extensive and magnificent structure” (p. 4), he is fine. He spends his time and money on decadent parties instead of helping his people.
When his dominions were half depopulated, he summoned to his presence a thousand hale and light-hearted friends from among the knights and dames of his court, and with these retired to the deep seclusion of one of his castellated abbeys. (p. 4)
The prince clearly saw the writing on the wall, and decided to protect himself and his friends and leave his people to die.
Quotes from: http://www.enotes.com/masque-red-death-text
In the story, the Red Death is a pestilence which has long plagued the country, leaving death and destruction everywhere it goes. Prince Prospero responds to this crisis by assembling one thousand of his friends from the surviving "knights" and "dames" of his court. Together with these friends, Prince Prospero travels to one of his "castellated abbeys," which is secluded enough to provide some sanctuary from the Red Death.
To ensure the most effective protection possible, Prince Prospero has built a strong wall around the abbey with a set of iron gates. The courtiers welded shut the bolts of the doors to make sure that nobody could enter or leave this place of sanctuary. It was, however, well-stocked with provisions to keep the Prince and his guests nourished and entertained.
The point of this extreme seclusion is to protect the Prince and his guests from infection, but, in an ironic twist, the Red Death is already inside and has come for the Prince himself.