A group of young men who work at an aviation factory begin to suspect that a doctor who runs an air ambulance service is secretly a spy transporting secret information from the plant to enemy agents.
The East Side Kids try to fix up a house for newlyweds, but find the place next door "haunted" by mysterious men.
A street kid has dreams of becoming a jockey. He gets his chance when he and his gang discover a poor old man who has a championship race horse. The man agrees to let the boy ride his horse in a race, but first the gang must get enough money to pay for the race's entry fees.
The gang is sent to the Wilton Reform School after they are unjustly convicted of stealing a truck. Bill Collins, brother of co-leader Danny, becomes involved in a killing and, while also innocent, is convicted and sentenced to death. Through a series of events, Muggs, Glimpy, Danny and the rest of the gang, learn that Knobby, a henchman of Luke Manning, knows something about the murder.
The East Side boxing champion Muggs answers a challenge to a fight against the West Side champ but just before the match he is kidnapped. His friend Danny Lyons takes his place and wins the fight, only to have Mugs believe that Danny was responsible for his kidnapping.
The East Side Kids find a young girl in the apartment of a man who has just been murdered. Believing her to be innocent, they hide her in their clubhouse while they try to find the real killer. The killer, however, used a baseball bat as his murder weapon, and the bat has the fingerprints of one of the gang on it.
A group of delinquents on their way to summer camp get stuck in a haunted house.
After living all his childhood in the street, a young boy rapidly notices that crime doesn't pay, leading him to become a policeman. One day, one of his best friends goes to prison for a murder he didn't commit. The policeman tries his best to release the friend by proving his innocence.
Rejected by the Army, Marines, and Navy for being too young, the punks help the war effort by throwing fruit at a shop they believe is owned by a Japanese American. Confronted by him wielding a short sword, the gang decides to come back at night but find him dead.
The East Side Kids discover that one of their own, Danny, is torn between staying and school and becoming a boxer, and is getting mixed up with gangsters.
Danny helps to capture a wanted criminal and receives a $200 reward. However, he has a falling out with the gang when they believe he should share the money with them. Complications ensue when the crook that Danny helped capture escapes from jail and comes looking for him.
Muggs, Glimpy and the rest of the Kids set about to Americanize affable young French refugee Jean Rogers. But after a disastrous baseball game, Jean is chased out of the neighborhood and told not to return.
Street kids get sent to the country, where they get mixed up in murder and a haunted house.
Muggs is tricked into entering a Civilian Conservation Corps camp by Danny in order to get in shape. Muggs resists and battles with the camp captain and with other campers. He also becomes involved in trying to help one of his friends get out of trouble.
After having been framed by gamblers, Muggs is barred from riding in horse races. Snce he can no longer race, he takes up a collection so Ma Brown, who owns the horses won't have her stable foreclosed on. However, one of the gamblers involved in the frame falls for Ma Brwn's daughter, and decides to come clean and confess to the police about the frame. The other gamblers hear about it and set out to shut him up and discredit Muggs and Ma Brown once and for all.
The police commissioner asks some local street kids to toughen up his ballet-loving son.
Copy boys Muggs and Glimpy investigate a murder. They locate the ex-wife of the murdered man and become convinced she is innocent. They hide her from the police while they investigate.
The East Side Kids are pursued by killers seeking a stolen necklace.
The gang is friend with a millionaire because they saved him from an agression. However, the gang is suspecting that the man's son was actually one of the agressors.
Muggs and Glimpy, two East Side Kids in the army, return to their neighborhood, supposedly on furlough; actually, Muggs has been honorably discharged with a physical defect, but he tells no one of this. Danny, another East Side kid, is in jail because a large amount of medical supplies have been stolen from the warehouse where he works. Muggs see Spider, a new member of the gang, flashing a large amount of money around, and Muggs shrewdly turns toughie, boasting that he has a dishonorable discharge because of thievery. This leads Spider to confide in Muggs that he is the one who has been aiding in the theft of supplies from the warehouse, and he gets paid for the loot by Larry, operator of a nightclub where Muggs' sister, Milly, is an entertainer. Fingers, a henchman for Larry, kills Spider when he learns that Muggs has been let in on the operation. The police then suspect Muggs of killing Spider.