24 year old Gordon Carbhoy (Ray) has spent $100,000 on wine, women, and gambling, and must confront his father. In three years as his secretary he has only spent, not made, money. An intertitle reveals that the young man is made of the same steel as James Carbhoy (Charles French), but is as yet untested by life. Gordon challenges James: give him $5,000 and he will turn it into $100,000. But there is an important caveat: Gordon will not play by James's "Sunday School" rules of business.
Heading for the Yukon, he is thrown off a train after starting a fight with another passenger who is cheating him at craps. Snake Falls, Montana, where he lands, seems unpromising, but Gordon's luck has just begun. Giving his name as "Hackett," he learns there is talk of a land boom, because a nearby coal mine will require construction of a train station. Befriended by Silas Mallinsbee (George Nichols), and smitten with his daughter Helen (Vola Vale), a western girl comfortable on horseback, Gordon decides to help them secure the building in nearby Buffalo Point. David Slossom (Robert McKim), who holds the railroad's decision in his hands, tries to use this power over Helen. When he fails, he attempts to rape her, and Gordon arrives back just in time. A vicious fight ensues, in which it appears for a few moments that Gordon has killed Slossom, but he is only injured.
Gordon fears his prospects for showing his financial skills are lost, and he imagines, literally, his sack of gold taking wings in his mind, as seen in a superimposition. Then Gordon learns that his father is the other possible rail partner—and at once, "anything goes." Revealing his true identity to Silas, Gordon abducts Slosson (who, in a split-screen nightmare, had seen himself beaten by Gordon). Then, when James arrives, he is abducted, and Gordon sends a telegram in his father's name to begin construction at Buffalo Point. The real estate boom begins. Gordon stages his father's rescue, who is not fooled for a moment, but must live up to his end of the bargain with his son.
Meanwhile, Slosson has been put to work digging on the railroad. Only in the "happy ending" and keeping business ethics in a light-hearted vein does The Son of his Father, with its rather tongue-in-cheek title, conceal the more serious underlying questions of fair play and changing generational standards.