Werewolf takes place in a small village which is hunted by werewolves.
Each player is secretly assigned a role - Werewolf, Villager, or Seer (a special Villager). There is also a Moderator player who controls the flow of the game.
The game alternates between night and day phases. At night, the Werewolves secretly choose a Villager to kill. Also, the Seer (if still alive) asks whether another player is a Werewolf or not. During the day, the Villager who was killed is revealed and is out of the game. The remaining Villagers then vote on the player they suspect is a Werewolf. That player reveals his/her role and is out of the game.
Werewolves win when there are an equal number of Villagers and Werewolves. Villagers win when they have killed all Werewolves. Werewolf is a social game that requires no equipment to play, and can accommodate almost any large group of players.
Werewolf can be played online at BGG in the Werewolf Forum: http://www.boardgamegeek.com/forum/76/forum/1
There are several published versions of Werewolf, each of which contains unique characters, voting rules, and additional variants. Many rethemed versions are also available. This game is also known as Mafia.