Recent college graduate Jay Shaw masters a switchblade, adopts the pseudonym Phil Beldone and moves to a notorious Brooklyn neighborhood to infiltrate a gang, the Barons, so that he can write a book about juvenile delinquents. The Barons require that he complete a three-step initiation. First he must run a gauntlet of their members; secondly he must win the heart of a "deb," a female gang affiliate; and finally he must murder a chosen victim. He runs the gauntlet unscathed and romances Filene, but when the gang plans to roll and kill a fleabag derelict, Phil intervenes to save the old man, then convinces gang-leader Tiger that he should usurp Candle's war commander position, angering Candle. Candle and Fish break into Jay's hotel room and steal his bankroll, along with his notebook about the gang. When Tiger reads the notebook to the gang, they label Phil a rat and stool pigeon. He is set up to take the rap for a gang crime, but Filene bails him out. Just outside the jail, he meets Filene, but Candle and Fish ambush them, telling him that it was Phil's bankroll that they gave to Filene for the bail money. They try to knife Phil, but Filene defends him, taking a fatal stab. Police cars swarm into the area, apprehending everyone.
—Lew Amack