Isadore "Izzy" Goldberg changes his name to I. Patrick Murphy because his store is in an Irish-neighborhood in New York City. He meets Eileen Cohannigan, the daughter of a meat-packer, and he tells her he is Irish and a romance begins. When America enters World War I, "Izzy" enlists, is sent to France, and is wounded while engaged in a heroic rescue during a big battle. While recovering in an overseas hospital, he writes Eileen and tells her he is Jewish and not Irish. Returning home, he is parading with his regiment and he sees Eileen with Robert O'Malley, his old rival. He thinks she has thrown him over because he is Jewish. An Irish lodge comes to bestow an honor on the man they think is Patrick Murphy, an Irish hero. But O'Malley tells them his real name is Goldberg. But Eileen tels him it is he she loves, and they head for the marriage-license bureau.

"Matches Mary" has sold matches on the streets of New York for many years and nobody knows her real identity. The truth is that Mary's young son had been kidnapped many years ago and she donned ragged attire while searching for the man, whom she knew, who did it. Years later day she meets him on the street and demands to know about her son, now grown to manhood. The man, now calling himself Foster, escapes but Mary track him to his home. Foster's nephew comes in and announces that he has gotten married while in college. Foster is furious and threatens violence. That night he is found murdered and Peter is accused of the crime, and is put on trial. Mary testifies she was the one who murdered Foster. She is about to be sentenced when a detective brings in a confession from two burglars who admit killing Foster. Peter asks Mary who she is and she replies she is just "somebody's mother." Later, an old friend and a lawyer bring evidence that reunites Mary with her lost son, Peter.

The gang is participating in a program sponsored by the Golden Age Dramatic League. They present their own fractured version of Quo Vadis. Things go from bad to worse when the neighborhood tough kids disrupt the show. The pie fight is given a new twist by use of some slow motion sequences.

Joe Regan, a kindly traffic cop, comes home with presents for Jerry Murphy, his young ward, and discovers that the boy has been hit by a car. The doctors advise a sea cure, and Joe takes Jerry to a seaside resort, where they meet Alicia Davidson.

Mickey overhears the gang rehearsing a play and thinks it's real.