The local mob is killing off the small operators who are horning in on their gambling business. Nick flashes some cash and gets invited to one of the mob's casinos where he plays like he's a tough guy. This catches the boss' eye because he's always looking for new thugs.
Nick works undercover on a bank robbery. After the thieves are apprehended, the $100,000 they stole is nowhere to be found, and the police lieutenant who apprehended them is accused of taking the money. Now Nick works to prove the lieutenant innocent.
Nick wants to get hired by a gang planning on cleaning out the vault at a jewelry store. He makes sure he's seen as a flashy thug who needs work after a dame (who works for them) slips him a mickey and cleans him out.
A mobster just released from prison finds that his former protege now controls half of his old territory. Nick goes undercover to infiltrate the ranks of both men in order to get the evidence against them and prevent a major gang war from erupting.
After a boxer is killed for not throwing a fight as ordered, Nick goes undercover by taking over as manager for another young prizefighter, planning eventually to get him to turn evidence against the crooked promoter who ordered the killing.
A police detective vanishes after he is accused of robbing a train and killing two employees. Nick is sent undercover to determine if the officer is really guilty, or if he is even alive, and bring whoever is guilty to justice.
After a polished blackmailer drives one woman to suicide, Nick goes undercover to stop the man from his next target, actress Laura Crane. The blackmail scheme involves the suspicious death of Laura's first husband.
A shoe shop owner witnesses a mob murder, and Nick assumes the identity of the hit man who's been sent for to kill him. But the witness goes into hiding, and so the mob decides to smoke out the old man by using his wife and brother. Nick must act carefully to protect all three.
Posing as a businessman representing an electronic firm, Nick gets in with a mayoral candidate who's part of the mob. He offers Nick some free city land if he'll help frame the current mayor with a phony bribery set-up.