In June of 1934, newly-divorced Glynis Hampton and Woodhill Fire Department Captain Freddy Pratter find they share an interest in photography. They start going out on Sunday afternoons to snap pictures, and Freddy builds a darkroom in his apartment for developing film. Dalebridge Fire Chief Max Roper asks Freddy to investigate some field fires that Max believes were started by disgruntled farmers. Dalebridge firefighters Joe Lindbloom and Charlie Cooper, also are present. Shortly afterward, Glynis' brother, Mark Barneshill, who lives on his family's dairy farm, and is also a Dalebridge volunteer, warns Charlie to stay away from Glynis, making an enemy of Charlie. Another field fire is set in Dalebridge. Then, a suspicious fire in an abandoned barn in Woodhill is followed by a fire in an abandoned house where the body of a man is found in the basement. Joe Lindbloom, having helped Charlie set the first field fires, tells Charlie he will no longer help him. In turn, Charlie threatens Joe that if he doesn't continue to help, Charlie will make sure Joe is blamed for the death of the man in the basement. Mark and his father, Ben, argue and Mark takes off. That same night a farm fire in Woodhill results in the death of a child. Joe accuses Charlie of setting that fire and Charlie puts the blame on Mark. One afternoon when Glynis is alone in Freddy's apartment developing film, she sees an ad for an impotence cure. That same day, Freddy learns that Glynis' ex-husband is a homosexual. When Freddy and Glynis confront each other with their newly-found knowledge, each is mortified, and an argument ensues. While setting another fire, Charlie tells Joe that he can easily abduct Joe's wife or daughters if Joe implicates Charlie in the fires. After that fire is extinguished, Charlie further taunts Joe by suggesting that Joe's wife ran off with Mark. When Joe realizes that Charlie has been inside his house, he and Charlie fight. Charlie boasts that he is going to make sure Mark dies in a fire at the Barneshill farm. Joe tries to warn Ben, but is too badly injured to make himself understood. As Glynis drives Joe to the hospital, Joe admits his part in the fires. In the meantime, Charlie sets a fire in the Barneshill's dairy barn and lures Mark into the lower level of the barn thinking the upper-level floor will collapse, crushing Mark to death. The floor holds, Mark is rescued, and Charlie attempts to escape using Glynis as a hostage. Glynis manages to break free and Charlie is caught. Following Charlie's arrest, Freddy and Glynis make up and explain their reasons to each other for keeping their friendship platonic. As soon as they separate, though, they each regret their words. The next day, Freddy asks Glynis to marry him and she joyfully accepts.