From the publisher's website:
One Night Ultimate Werewolf is a fast-paced game where everyone gets to be a different role. In the course of only one night and the following morning, the players will determine who among them is a werewolf...hopefully. One Night Ultimate Werewolf is a microgame of the party game Ultimate Werewolf that doesn't need a moderator. There's no elimination, and each game lasts about 10 minutes.