Plot

Rookie New York cop has to deal with juvenile delinquents, his superiors, and blame for the suicide of a woman who jumped to her death while he was in her apartment.

In a particularly rough neighborhood of a major city, rookie patrolman Johnny Dean is assigned to replace Gus, a sergeant who is retiring. Gus introduces Johnny to most of the characters who live and work on the principal street and advises him not "to make waves." After Johnny, an idealist, quickly runs afoul of Leon, who owns a saloon and controls all of the illegal activity on the street, Gus warns him that Leon has powerful connections in the city government and can "fix" any charges brought against him and his friends. Tom, Leon's younger brother, and his girl friend, Nancy Kominski, along with Tom's pal, Ricky, also plan to cause trouble for Johnny. Later, when Johnny is forced to arrest Terry Warren, an attractive, alcoholic divorcée, for public drunkenness, she becomes infatuated with the young officer. After Larry, the teenage son of a storeowner, commits suicide under mysterious circumstances, Johnny attempts to discover the cause. When he visits Leon's saloon, Johnny finds the underage Nancy working there and sends her home. In retaliation, Nancy asks Ricky, who is attracted to her, to help her remove Johnny from the beat. That night, hoping to impress Nancy, Ricky leads a gang of hoodlums as they destroy a number of cars and break store windows on the block. Later, Nancy tries to persuade the lecherous Leon to give her a job in his modeling business where Ricky's sister Joan works. After she is released, Terry helps Johnny when he is attacked in an alley by Ricky's gang and then invites him to dinner at her place. Nancy, meanwhile, experiences a change of heart about Johnny and also expresses a romantic interest in him. The food Terry prepares is spoiled as she has been drinking again and, when she tells Johnny that she wants to marry him, he gently rebuffs her. Adding to her woes, Terry's ex-husband appears seeking a copy of their divorce decree as he intends to remarry. The realization that she is constantly failing pushes Terry to climb out a window onto a ledge high above the street and, despite Johnny's promises to help her, jump to her death. As Johnny was present at Terry's death, he is suspended pending a hearing, but he continues his investigation into Larry's death and learns from Nancy that Larry and Joan used to go steady and that Joan "outgrew" him when she became a model. Johnny also talks with Larry's friend, Short Stuff, who tells him that Larry had discovered that Leon's modeling business was simply a front and that Joan was actually a prostitute. When Johnny goes to talk with Joan at her apartment, she is not there, but he is able, in her absence, to convince her roommate, Frances, to testify about Leon's criminal activities. After Joan returns and discovers that Frances has informed on Leon, she alerts him. Johnny visits Gus and, after informing him what has been happening, asks him to tell the authorities about Leon's political connections, but the old sergeant is noncommittal. Gus then warns Johnny that both Frances and Joan are in great danger. Meanwhile, in order to impress Leon, Ricky agrees to kill Frances, but Nancy overhears their conversation and informs Johnny. When Johnny is unable to find Frances, he takes Ricky to the precinct station and attempts to book him in order to interrogate him, but the desk sergeant refuses to cooperate and Leon intercedes on Ricky's behalf. Eventually, Johnny learns from Nancy and Short Stuff that Ricky was seen driving Frances into a deserted garage, owned by Leon, then leaving without her. Johnny forces Leon to accompany him to the garage, but when he can find no trace of Frances, Johnny releases Leon. Later, Johnny returns to the garage, followed by Gus who pleads with him to stop his investigation. After Gus leaves, Johnny looks under Ricky's car and discovers an opening to a water-filled sewer underneath. Leon then suddenly appears and shoots at Johnny, causing him to fall into the opening. When Johnny grabs onto the surrounding rim, Leon stomps on his fingers. Gus, who has had a change of heart and returned to the garage, shoots Leon, who falls past Johnny into the sewer and is drowned. Gus then helps Johnny to his feet. Later, Johnny is reinstated and returns to his beat on the mean streets.