Warning: wikipedia contains spoilers
The plot concerns two middle-aged petty criminals, Charlie and Brian, who are about to part company with their gang because they dislike violence. By a farcical turn of events, they end up with the loot from their last job and the rest of the gang on their tail. The only place they can find to hide is a convent, and they dress up as nuns and pretend to be new teachers.
Much of the comedy comes from Charlie's efforts to teach Brian how to behave like a Catholic, and by both men's attempts not to be distracted by the presence of so many teenage girls. Meanwhile, Brian has fallen for an extremely short-sighted girl who attempts to help them escape from their pursuers.
The money ends up in safe hands.