In their first film, the Bowery Boys tackle gangsters.

Because of his quick temper, New Yorker Slip Mahoney loses job after job, exasperating his sister Mary. After he is fired from a flower delivery job, Slip and his friends, Sach Jones, Bobby, Homer and Whitey, watch a salesman selling stain remover on the streets, and Slip, thinking that this is an easy way to make money, asks the salesman to cut him in on the business. At first, the salesman refuses, but when he learns that the police are on the way to arrest him, he agrees to sell the remaining bottles to the boys for ten dollars. Slip then prepares to demonstrate the remover by spilling ink on the jacket of a passerby, and when he is unable to remove the stain, picks a fight with the man. Slip is trounced, but Sach manages to win back their money by placing bets on Slip's opponent, whom he has recognized as a former lightweight champion. The following day, Slip applies for a job with Herbert Sayers, Mary's boss. Although Slip is sure that he will be hired in a managerial position, he is ordered to begin work at the bottom, shoveling dirt on a construction site. Once again, however, he gets in a fight and loses the job. In a last attempt to hold down a job, Slip joins Sach, who is working as a "skip tracer," repossessing goods from people who are behind on their payments. His first assignment is to take back a car from a singer named Jeanette, who works at the High Hat Club. At the club, Jeanette offers to get Slip a different job with her friends if he agrees to overlook her debt. When he arrives at her apartment to meet her friends, he sees a photograph of Sayers, Mary's boss, on a table. Jeanette claims that she and Sayers are no longer involved, but Slip is skeptical. Jeanette does not really intend to find Slip a job, but plots to have him killed. While they are driving to a meeting with the men who will commit the crime, however, Slip manages to repossess her car. Slip is so successful at his job that his boss, Barton, asks him and Sach to serve summons on Patsy Clark and Pigeon, who are being charged with running an auto theft ring. Meanwhile, Sayers asks Mary to come to Mexico with him on business. Assuming that Patsy is a woman, Slip confidently sets off to deliver the summons. To his surprise, Patsy turns out to be an enormous man, who has no intention of allowing Slip to take advantage of him. Posing as an employee of Patsy's out-of-town gangster pal, Slip waits for an opportunity either to escape or serve the summons. While he is with Patsy, Slip learns that Pigeon is actually Sayers and is going to Mexico in order to avoid arrest. Eventually, Sach and the boys come to Slip's rescue, and the ensuing ruckus attracts the police, who arrest Patsy. Slip and the boys then hurry to the airport to stop Sayers from leaving the country. Mary is so proud of her brother that she punches Jeanette, who is boarding the plane, when she makes a disparaging comment about him. Slip is delighted and pronounces his sister "a real Mahoney."