The son of an alcoholic becomes a boxer and falls in love with the daughter of a prominent gambler.
Unemployed actor Brian McCoy (Frank Morgan) passes up a job, but his son Tommy (Gene Reynolds) makes a little singing and wins a $5 bet boxing. Fighter Johnny Martin (William Gargan) takes them traveling; drunk Brian does not send money to his wife, and they learn she died. Tommy goes from singing to boxing. Brian owes $600 from gambling to Jim Cain (Edward Arnold). Tommy McCoy (Robert Taylor) tells Cain he'll pay after he fights his mentor Martin, who is trying to come back. Martin tells Tommy he is broke and not in shape. In the bout Tommy doesn't use his right but knocks out Martin. Tommy takes the money and gives it to Martin's wife (Isabel Jewell) at the hospital, where Martin died. Drunk Brian got money from Cain; but Tommy tells his father he is quitting and slaps him.
Tommy is called "Killer McCoy" and can't find work. So he goes to Cain, who promises him 20% of side money. Tommy trains on Cain's farm and meets his daughter Sheila Carson (Maureen O'Sullivan), who thinks her father is an investment banker. Trainer Happy Lane (Lionel Stander) tells Sheila's friend Vivian (Jane Wyman) to leave. Brian arrives, and Tommy welcomes his father. Sheila and Vivian watch Tommy box and win as Cain wins a bet from Pug Walsh (Nat Pendleton). Vivian sends Tommy an invitation to the school dance. Cain thanks Tommy and tells him not to train at the farm. Tommy dances with Sheila, thinking she invited him; but Vivian informs him. Tommy gets rid of Vivian to be with Sheila. Bob gets jealous and tries to fight Tommy but falls in the lake.
Tommy wins matches and spends time with Sheila. Pug makes a large bet with Cain. In a bar Brian tells Pug that Tommy has a great right and that Cain has part of his contract. Pug and his men make Brian tell where Sheila is. On a sailboat Sheila asks Tommy to quit boxing, and they kiss. Sheila takes him to her father, and they pretend they have just met. Cain tells Tommy not to see Sheila again and closes his gambling business. Pug's men abduct Sheila and hold her with Brian. Pug bets that Tommy will lose in the 8th round. Tommy gets a note to lose in the 8th if he wants to see his father and Sheila. Tommy tells Hap he must do it. Guarded Brian and Sheila hear the fight on radio. Brian collapses and grabs a gun. Sheila leaves, and Brian shoots the two men and is shot. Tommy is saved by the bell in 6th round. Sheila rushes to the arena and tells her father she knows. Tommy sees her, fights hard, and wins, then says it is his last fight. In the final scene Tommy weds Sheila.
This well-made drama implies that boxing and gambling are a bad combination, which alcoholism makes even worse. Tommy might have been a singer, but it looks like Sheila is straightening him out after his father's bad influence.