Corey and Lassie visit the McKinnon ranch where there's conflict. Jim's parents want him to go to college, he wants to get a job and marry. Danger lurks as a cougar stalks the cattle, injuring Ben so Jim heads out with a rifle.
Jim returns from the army with intentions to marry rather than go to college and become a forest ranger as he had planned. When a cougar attacks his father, Jim tracks it alone. After Lassie and Corey save him, Jim decides to go to college.