Travis Coates, at fourteen, is in between boyhood and manhood when his father leaves on a cattle drive for several months, telling Travis to be the man of the house by watching over his mother and younger brother and doing chores without being told. Travis is determined to prove to himself—and to his family—that he is up to the task and deserves to be seen and respected as an adult.
He begins to doubt himself, though, when all sorts of things go wrong. His brother, Little Arliss, tries Travis's patience by romping in the family's drinking water with Old Yeller, a stray dog that Arliss has decided to keep. Arliss is also prone to telling tall tales about diving for huge fish and carrying snakes and fish in his pockets. It seems to Travis that his mother usually takes Arliss's side and reprimands Travis, making him feel like a child instead of the man he so desperately longs to be.
After Old Yeller rescues Arliss from a bear whose cub he had been trying to catch, Travis accepts the dog, who gradually becomes his own pet. Travis continues to fulfill his responsibilities as the man of the house by gathering crops, repairing the fence, and marking the hogs.
The most adult thing Travis does in the story is his decision to put Old Yeller down after the dog is bitten by a wolf with hydrophobia. Heartbroken, he also buries Old Yeller, and his father returns with a "man's horse" for Travis, which he has more than earned. Travis's definition of adulthood expands to include not only responsibilities but also consequences, foresight, and courage.