Each player controls a number of guests at a party, with the number of guests dependent on the number of players. These guests start the round in the spaces of the gallery on the game board, one guest per space; this initial placement is a large part of a player's strategy.
The Phantom (or "Hugo the ghost" in earlier versions) starts in the cellar, then climbs the stairs towards the gallery where the guests circle. The mechanism for the Phantom's movement is simple: On a player's turn, he rolls a special die. If he gets a number, he moves his pieces; if he gets a Phantom, the Phantom moves. This means that with more players in the game, the Phantom moves a lot more frequently, so you must adjust your strategy accordingly.
Once the Phantom has reached the gallery, the guests can start ducking into rooms adjoining the gallery to avoid him, with only one guest per room! A couple of rooms are special in that they add or subtract extra "fright points" from your score. As the Phantom catches up with the remaining guests, they are sequestered on the stair steps, then in the cellar. The first guest caught "earns" the most fright points, with those caught later in the round earning less and less.
Once all the guests have been caught, the fright points are tallied. After playing a predetermined number of rounds, the player with the fewest fright points wins!