Vermin first encountered Johnny as boy when they were both selling newspapers. Vermin tries to bully Johnny into leaving, as he wants the whole neighbor sell newspapers to, but Johnny defeats him in a fight. This fight catches the attention of Jocko Dundee, a local gangster, who hires Johnny as an enforcer.
Years later, during a gang war between Dundee and his rival Roman Moronie, Vermin and his sidekick, Dutch, join Dundee's gang. After Dundee retires and makes Johnny his successor, Johnny ends the gang war by calling a truce with Moronie who, thanks to Johnny's brother Tommy, is deported to Sweden, even thought Moronie says he's not from Sweden. After Moronie's deportation, Vermin and the corrupt D.A., Burr, plot to have Tommy killed, even after Johnny tells them not to. When Tommy survives their attempted to kill him, Johnny has Burr has killed and Tommy is made the D.A., which makes Vermin suspicious. Vermin goes to spy on Tommy's wedding and realizes that Johnny is Tommy's brother Johnny Kelly. After Johnny tells the gang he has decided to leave and give his criminal life, Vermin reveals that Johnny is the D.A.'s brother, much to their shock. Johnny then tells Vermin and the others he's turning in all the evidence to the crime commissioner. However, before Johnny can Vermin kills the crime commissioner. When Johnny discovers the crime commissioner dead, Vermin knocks him out, frames Johnny, and steals his cigarette case, which was given to him by Dundee. When Johnny is sentenced to death row and Vermin congregates Tommy, the latter becomes suspicious of Vermin after he sees him holding Johnny's briefcase and Johnny and Tommy's mother Ma punches Vermin's genitals, the cigarette case falls out Vermin's pocket and Tommy and Ma realize Johnny is innocent. After Ma gets evidence from a cleaning lady who saw in the building and Tommy plans to take Vermin to court, Vermin decides to kill Tommy the next night at a movie theater. The next night at the theater, Vermin cuts a hole through the screen intending to shoot Tommy through it. However, Johnny, who was informed of Vermin's plan to kill Tommy by a parrot sent by his girlfriend Lil Sheridan, escapes prison, arrives at the theater, and shots Vermin. After saving Tommy, Vermin is arrested while Johnny is pardoned the governor.
- As running gag throughout the movie, when someone does something to Vermin, he tells them they shouldn't do what they did to him, and says one of his relatives once did it to him.