Steve Kostain (Lund), nephew of the owner, begins working at a steel mill to learn the business from the bottom up. He rooms with a steel working family, the McNamaras, and falls for the daughter, "Red" (Sheridan), who is already involved with another steelworker, Jim (Duff.) Although he is at first has a hard time with his co-workers, he eventually wins them over, and also wins the girl.

Crew leader Jim Denko leaves work at the Kostane Steel Company and heads straight for the restaurant run by his spirited girl friend, "Red" McNamara. When he gets up from his huge steak dinner to wash his hands, Red derails a flirtatious customer by giving him Jim's meal, thus setting him up for Jim's ire. The customer, who unknown to Red and Jim is Steve Kostane, the nephew and heir of steel tycoon Mike Kostane, insults Jim upon his return, and the two exchange blows. Impressed by each other's toughness, the two make up, and Red, feeling guilty, buys Steve a new jacket to replace the one that ripped during the fight. Not knowing Red's last name, Steve mentions that he is boarding with a family named McNamara, and Red tries to discourage him by claiming that they are eccentric. Steve believes her until her meets her parents, Mac and Millie, and is welcomed with open arms as the nephew of Mac's old friend Mike. That night, Red is dismayed to find that Steve has taken over her room, while Steve is delighted to discover that they will be living in the same house. At dinner, Steve's upper-class girl friend Valerie calls and asks for "Steve Kostane," prompting Red to realize his true identity. He then unwittingly insults the family by speaking to Valerie disparagingly about his new working-class status. Red spurns his attempts to apologize, but when Jim arrives to take her out on a date, Steve offers to pay him double-time for a tour of the plant that night. All three go to the plant, where Jim details the process of steel smelting. The next day, Mac assigns Steve to Jim's crew, and Jim worries that the neophyte will slow them down, causing them to lose the monthly prize for highest production. Steve proves to be a hard worker, however, even though the work is difficult and dangerous. Later, Steve challenges Jim to a horseshoe game and wins the chance to go along on Jim's date with Red that night. When Red discovers that Jim has gambled away her company, however, she goes out alone with Steve. They end their date at Lover's Vista, where Steve charms and kisses her. One night soon after, Valerie visits and picks up Steve in a racy sports car. He returns drunk and, when Red puts him to bed, announces that he has broken up with Valerie. Red lets him kiss her but stalks out when he calls her by his pet name for Valerie. The next day is the last of the contest, and Steve's obvious hangover infuriates Jim. Steve struggles through the afternoon while their crew hangs on to the lead. When he sees Mac suddenly clutch his chest and fall, Steve races to help Mac, and by the time the older man has recovered, the furnaces Steve was stoking have overflowed. Steve instinctively runs to correct his mistake, and Jim has to save him from the furnaces' extreme heat. So many pounds of steel are ruined that they lose the pool, and though Mac offers to tell the truth to Jim, who has several personal bets riding on the competition, Steve refuses. At the restaurant that night, as the other crew collects their winnings, Jim angers Red by punching Steve. The next day, Mac informs a delighted Millie that he is ready to retire, but at the plant that afternoon, Steve witnesses him suffer a heart attack and collapse, falling into a huge barrel which is about to fill with molten steel. Steve courageously rides a crane into the barrel, saving Mac at the last possible moment. Red and Millie receive the news and run to the hospital, where they find Mac revived and Steve recovering from second-degree burns. Red tells Steve how proud she is of him, after which he informs Mac and Millie that he would like to be their son-in-law. Overjoyed, Red kisses him.