A fashionable gambling house at the Hotel Transylvanie. Lescaut, Pousette, Javotte, and Rosette are at the tables. There are signs that all the playing is not above board. Guillot enters and sings a risque song with gestures about the Regent and his mistress.
Manon makes her entrance with des Grieux. She urges him to play after she wrings from him a declaration of love so complete it puts his other avowals to shame.
Meanwhile, Lescaut has been cleaned out. Guillot challenges des Grieux, who wins. Guillot abruptly closes the game with the accusation that his opponent has been cheating and leaves the gaming room. Des Grieux will not escape as Manon urges; leaving would be an admission of guilt. Guillot returns with the police at his side. He demands the arrest of des Grieux as a cheat and Manon as his accomplice. When des Grieux makes a move towards Guillot, his father intervenes and tries to shame him into accepting the situation. The lovers are arrested. Des Grieux goes to prison, but is released quickly. Manon goes to trial and faces the near certainty of transportation as a lady of easy virtue.