A con man falls in love, gets put in jail, and decides to go straight; but an accident on their wedding day causes them both to do time.
Eddie (Clark Gable) cons a man out of $30 for a ring found in a wallet and gives his partner $10 as "half." Chased by the police, he runs into Ruby's apartment and hides in the bathtub. Ruby (Jean Harlow) gets rid of the police and takes $10, telling Eddie even his smile is crooked. At a restaurant Ruby pretends to lose her purse. Al (Stuart Erwin) finds out but gives her money anyway. Eddie dances with Ruby and cons Al out of $10 in dollar-bill poker, giving Ruby $5. Slim comes in with friends, and Gypsy (Dorothy Burgess) gets jealous of Ruby. Slim has a quick job for Eddie that lands him in jail for two months. When Eddie gets home, Ruby has fixed up his apartment. Slim and Eddie plan to clip a man who wrote to Ruby; but Eddie throws the man out and gives him his ring back. He tells Ruby they are going for a marriage license, and she does not object. However, the man is found dead in the hall. Ruby is arrested and put in the reformatory for two years, while Eddie disappears.
In the reformatory Sadie, a socialist, criticizes society's injustice. Ruby meets Gypsy, and they slap each other. Gypsy says Eddie sent her $10 for Christmas. Ruby is pregnant, and Gypsy gets out. Al visits Ruby and asks to marry her, which would get her paroled. Ruby tells the matron Al is too good for her. Ruby takes the blame for Sadie ripping a hymnal and loses her visiting privilege. Ruby sings, "Hold Your Man." Gypsy visits Ruby and tells her Eddie cares about her, realizing that Ruby sent her the $10. Eddie visits his "sister," Bertha. Ruby is removed for her violation, while Bertha hides Eddie. Authorities are looking for Eddie, but he meets a black preacher visiting his daughter and asks him to marry Ruby and him. Sadie has keys and gets Ruby out of solitary. Eddie kisses Ruby and says he's been going straight since they got the license. Eddie and Ruby are wed as the police break in and arrest him. Ruby cries and says Eddie meant no wrong. In the final scene Eddie is met at a train station by Ruby and their son. She tells Eddie that Al has a job for him.
These two con artists get stuck on each other and come to realize that to be together they will be better off going straight. They prove their love for each other by not giving up even when separated by imprisonment.