Spoilers of the Forest

When Montana lumberman Big Jack Milna and his wife are killed in a forest fire, Milna's partner, John Mitchell, becomes the guardian of their orphaned daughter Joan and takes her to live with his wife Linda and son Billy in the vast, timbered expanses of the Flathead Forest that he had just bought with Milna. Over the next fifteen years, John, a staunch conservationist, cuts only enough trees to cover the family's living expenses and taxes. When John begins to suffer from heart problems, making it difficult for him to work, he decides it is time to sell off one sector of the forest, and consequently, lumber magnate Eric Warren and his foreman, Boyd Caldwell, come to Flathead to make an offer. Warren, a ruthless businessman used to getting his way, wants to log the entire forest, but John refuses to accept his terms, arguing that the forest should last forever and not be sacrificed for callow greed. The hospitable John invites Warren and Boyd to join the family and their close friend, logger Tom Duncan, for dinner, and after the meal, Warren unexpectedly agrees to contract for just one section of the forest. As Warren and Boyd drive back to town, Warren outlines his plan to woo Joan, who owns half the forest, over to his side by exposing her to "the good life." Warren also instructs Boyd to romance Joan, and soon after, Boyd goes to work by inviting Joan to visit the logging operation with him. As Joan takes Boyd to a pristine spot by the lake, Billy, who has signed on as a logger for Warren, breaks his leg when a safety cable breaks, sending a heavy log crashing down on him. After an ambulance takes Billy to the hospital, Williams, a forest ranger, wonders whether Warren is following safety procedures. Beginning to question Warren's motivation, John warns Joan to be wary of Boyd. Warren, meanwhile, encourages Joan to charge whatever she wants, and after she acquires a fancy new car and contemplates buying an expensive house, Boyd begins to feel guilty about deceiving her. Soon after, Warren's glamorous wife Phyllis comes to visit and quickly befriends Joan. After Phyllis returns home to San Francisco, a careless trucker speeds his truck along the rutted logging route, causing the chains binding the logs to snap. Although Boyd tries to warn the trucker, the steep grade renders the vehicle's brakes useless and, as a result, the logs spill out, starting a fire that kills Duncan. Blaming his friend's death on Warren's greed, John denounces Joan's friendship with Warren and Boyd. Defying John, Joan announces that she is going to San Francisco to visit Phyllis, and that when she returns, she plans to move into her own house. In San Francisco, Phyllis throws a party in Joan's honor at the Warrens' opulent apartment overlooking the bay. Although pretending to be her friend, behind Joan's back, Phyllis and her snobbish friends refer to the guest of honor as "the timber queen." After the guests leave, Boyd tells Joan that Warren bought her the house she wanted, then they kiss. Joan returns to the Mitchell's bearing gifts, and when she invites them to live with her and her servants at the new house, John unequivocally rejects the offer. As they finish cutting the contracted section of forest, Warren spurs Boyd to persuade Joan to sign a contract giving them access to the rest of the forest. One day, while Warren, Boyd and some loggers are surveying the uncut area, John spots them and orders them off his land. Warren cruelly informs John that he is expecting Joan to sign a contract allowing her share to be cut, then chides him about the futility of preserving the woods. When one of Warren's men pulls out a gun, Boyd avoids a confrontation by agreeing to leave. As they walk to the car, Boyd looks back and sees that John has crumpled to the ground in pain. After sending Warren and the others ahead without him, Boyd returns to help John. Later, as Joan and Boyd await the Warrens' visit to Joan's new house, Boyd tells Joan that he loves her and wants to marry her. When the Warrens arrive, Warren hands Joan an itemized list of the money that she owes, then presents her with the contract. After Joan refuses to sign it, Warren informs her that she has spent her entire income. Warren is flabbergasted that Boyd supports Joan's decision, then, when Boyd announces that he and Joan plan to be married, Warren accuses Boyd of trying to gain control of the forest for himself and tells Joan of their scheme to entrap her. Warren then slugs Boyd, and when Boyd hits back, Phyllis enlists their chauffeur to defend Warren. After handily defeating both men, Boyd learns that Joan has fled. At the Mitchells', a contrite Joan apologizes to John, who forgives her. As the logging company prepares to leave the area, Billy drives one of the last trucks down the mountain. When his brakes fail, Boyd leaps into a jeep with logger Pat Casey and speeds after him. Pulling up alongside the truck, Boyd yells for Billy to jump into the jeep, and seconds after Billy jumps, the truck careens out of control and crashes. Back at the Mitchell house, Casey praises Boyd's heroism to John, prompting him to change his mind about Boyd. Just then, Boyd drives by the house and Joan runs after him to express John's gratitude for saving Billy.