From the Game's Introduction:
The players will take on the roles of the hosts and guests of a lavish party, an extravagant affair that takes place within the walls of a grand mansion while a plague sweeps across the country outside. However, as you may well know, and will surely learn, death may not be held in check by iron gates and stone facades, nor by purses full of gold and goblets full of wine. This will be the tale of how even the noblest fall to the pestilence, and how the reaper takes his due on all men.
In the beginning, each player has a single six-sided die in one colour (ideally white) with the exception of whoever is playing the host: they get a die of a different colour (ideally red). Starting with the host, players take turns to describe the events of the party and then roll their dice.
If any player rolls a 1, they have succumbed to the plague. They hand their dice to another player who narrates finding the body. The player with the red die narrates the discrete disposal of the body and then passes the red die to another player (taking as replacement a spare white die).
Play continues, with the events of the party becoming more extreme, and an increasing number of revellers dying from the plague, until all the characters are dead and death wins the game.