Slim (Warner) is a story of electric linemen, the high-wire workers employed in constructing and repairing the country's power lines. With minimum resort to dramatic contrivance, it presents certain interlocking episodes in the lives of Linemen Red Blayd (Pat O'Brien) and Slim (Henry Fonda). It begins when Slim, a farm boy fascinated by the hazardous function of the linemen putting up a transmission tower, asks for a job; it ends, after Red falls to his death in a high-wire accident, with Slim climbing a tower in a blizzard to resume the repair job thus interrupted. Told with a drawling, mournful humor, the film builds up to a little epic in the sardonic idiom of one of the world's most necessary, most dangerous, least publicized trades.
Slim got his job because a butter-fingered lineman dropped a condenser and got fired. Red Blayd liked him. Red was independent as a king. He was the most respected man on that power job. He could have been a construction boss, but preferred a footloose life, wandering from one line job to another, working until he had a roll and then living high until he had to go to work again. First Slim was Red's "grunt" (groundman). Slim sent up tools as needed on the hand line, tossed up bolts which Red caught with the nonchalant magnificence of a big-league outfielder. When a lineman with a hangover dropped off a tower and got killed, Slim stopped being a grunt. He was so proud of his lineman's belt he hated to take it off at night. Because Red wouldn't stand for any big lip from the man sent to investigate the accident, he and Slim headed Red's old car for Chicago.
Cally (Margaret Lindsay) was a nurse who had taken care of Red when he was hurt once. In Chicago, he always looked her up. Cally taught Slim to dance. Talking to Red was no use, but Cally tried to get Slim to quit line work. Slim turned down Cally's plea. He strung along with Red.
On their next job there was a fight. Wilcox (Joseph Sawyer), a lineman jealous of Red's prestige, tried to loosen the line that was dropping Red. Slim got to Wilcox in time. He and Wilcox were both hurt. When Slim wrote the news to Cally, she came out to nurse him. She fixed it for him to have a job in maintenance, where he could stay put and raise a family. Once more Slim thought he'd go with Red, so Cally called off their wedding. Climax in the contest between love for Cally and the job of being a lineman came in the power-house yard on a snowy night, with the ends of hot wire, broken by the cold and the weight of ice on them, flapping in the wind till the high voltage lines nearby, on which they struck, short-circuited like torches, with the blast of a million electric chairs, That was when Slim, after Red's body fell across the wires and exploded like a fuse, left Cally and went up the tower again.