Out collecting for the poor, Sister Bertrille finds some men shooting craps. To get rid of her, Juan, a loser, tosses a dollar in the basket. He has a winning streak and splits his winnings with Sister Lucky. Mother Superior, however, insists that Sister Bertrille return Juan's contribution before Bishop Parnell's visit. Juan won't take it back even though Sister Bertrille tries to explain it was just probability at work. Sister Bertrille finances Manuel to shoot craps with Juan to convince him. After many passes, Juan, with most of the money, is sure Sister Bertrille is lucky for him. The police break up the game and Sister Bertrille goes to jail with the others. Mother Superior finds it hard to explain when the Bishop sees Sister Bertrille emerge from the paddy wagon. Captain Lopez wants Sister Bertrille to leave, but she refuses unless the others are released from jail too. Carlos Ramirez arrives to get her out and declares Juan is just a gambler. Sister Bertrille feels Carlos is a gambler too, but he explains he's a businessman. With a legal casino, the odds are always with him and he can't lose. Juan insists he can't lose either. To prove she's not Juan's lucky charm, Sister Bertrille agrees to leave jail if Captain Lopez allows Juan and Carlos to play blackjack. With Sister Bertrille at his side, Juan breaks the bank and Carlos admits defeat. Mother Superior phones that Bishop Parnell, a family friend, wants to see Sister Bertrille. She flies to the convent and finally getting away from the Bishop, finds that Juan has gone broke. With her return, he gives Carlos a marker and play resumes. Losing, Juan admits his marker is worthless and Carlos threatens a lawsuit. Sister Bertrille suggests that he give Juan a job, so he can work off his gambling urge and his debt to Carlos, in the casino.