Roy 'Slag' McGurk, [Wallace Beery], a former heavyweight boxing champion, ekes out a living as a bouncer in the Bowery, working at the saloon run by Edward Arnold Mike Glenson. When Mike must meet two brewers for a major deal, he sends Slag to fetch his daughter, Caroline Glenson, who has just returned from Europe. Although estranged from his former boxing protégé, Johnny Burden, who has joined the Salvation Army after a hard-fought match left another man wheelchair-bound, Slag tries to explain that Mike sent Caroline away to try to drive a wedge between them.
At Ellis Island, an associate offers to pay Slag to round up 50 new immigrants to work for him. The fiftieth recruit is a young English boy, Nipper, an orphan who has been sent to America to live with his uncle, Milbane. Slag reluctantly agrees to take the boy, who would rather stay with him than go to Milbane. When rival recruiters clash, Nipper either loses or discards Milbane’s address tag. After searching for the uncle, Slag ends up keeping the boy and a stray dog that Nipper saved from the dogcatchers.
To complete his deal with the brewers and to build the biggest saloon in the Bowery, Mike needs the Salvation Army building cleared out. He orders Slag to move the group, but Slag refuses. Mike then blackmails him, claiming he has evidence that Slag’s championship bout was fixed and that the opponent took a dive. To placate his employee, Mike offers to make Slag a partner in his new saloon for $2000, a sum Slag hopes to win as a reward from Milbane’s side.
Meanwhile, the Children’s Protective Society learns about Nipper, and the only way Slag can keep the boy is to join the Salvation Army, under the leadership of Johnny Burden. When Slag finally locates Milbane, he discovers that Milbane is a crook who wants the boy for money. Nipper, hearing their loud argument, learns that Slag’s interest is only in the reward. The heartbroken boy goes to stay with the Salvation Army, and word gets around, causing Slag to lose the friendship of Mamie Steeple [Aline MacMahon], who had been lending him money for years.
Mike pushes Slag to stage a riot at the Salvation Army, but Slag rebels. He tells the saloon patrons that his championship bout was rigged, then fights the mob he had recruited for Mike. Johnny joins in, and together they defeat the gang arrayed against them. Caroline discovers what her father tried to do and begins to pack her things. In the end, Mike yields, telling Johnny to go after her. With a clear path to adopting Nipper, Slag asks Mamie Steeple for a loan of $200 ... to pay for a wedding.
