Sister Monica Joan is found wandering near the docks, and returned to Nonnatus House by the police. Her adventure takes its toll on her health and she succumbs to pneumonia. When she eventually recovers she sails forth back into the community only to find herself in trouble with the law when she is accused of theft. As Sister Monica Joan's case progresses to trial the Nonnatus House community fears that the old nun could find herself going to jail. Chummy has further worries when her mother decides to make a trip to inspect her new beau.