The novel focuses on the young life of Duddy Kravitz, a poor Jewish boy raised in Montreal, Quebec. Family, friends, lovers and teachers all contribute to Duddy's burgeoning obsession with power and money — desires embodied in the possession of land. As a child, Duddy is told by his grandfather that "a man without land is nobody," and Duddy comes to believe land ownership to be life's ultimate goal and the means by which a man becomes a somebody.
Duddy begins to move towards this goal by working for his Uncle Benjy. Their relationship is strained: Uncle Benjy, a wealthy clothing manufacturer with socialist sympathies, has always favored Duddy's brother Lennie, who wants to become a doctor. Uncle Benjy takes a dim view of Duddy's commercial ambitions, seeing them as avaricious and crass. During the summer after high school, Duddy takes a job as a waiter at a hotel in Ste. Agathe. He stumbles upon a beautiful and secluded lake while out with his soon-to-be lover and "Girl Friday", Yvette. A born entrepreneur, Duddy immediately sees that the lake has tremendous potential as a summer resort.
Duddy returns to Montreal and starts a company to produce bar mitzvah films. To this end he hires Friar, an alcoholic, avant-garde filmmaker blacklisted in the United States, for his communist tendencies. Since Duddy's childhood, his father, Max, had told him stories about Jerry Dingleman, the local "Boy Wonder" whose rags-to-riches story is canonical among the residents of St. Urbain Street. Looking for help with his film company, Duddy attempts to engage Dingleman. The two travel to New York City, but Duddy fails to secure any assistance from the "Boy Wonder", who sees Duddy as a naive upstart and uses him to ferry a package of heroin across the Canada-U.S. border.
On the way back from New York, he does, however, meet Virgil, an amicable and trusting American with a consignment of pinball machines for sale. Back in Montreal, Duddy rents an apartment and an office for himself and Yvette and begins buying up the plots of land around the lake he yearns to possess.
After Friar tries unsuccessfully to seduce the comely Yvette, he wordlessly and suddenly abandons his work with Duddy. Duddy rebounds by starting a new movie distribution business and hires Virgil as a travelling projectionist. A few months later, Virgil, an epileptic (a fact known to Duddy when he gave Virgil the job), experiences a seizure while driving, crashes and is paralyzed from the waist down. Yvette, blaming Duddy for the accident, takes Virgil to Ste. Agathe, where she cares for him. Duddy is left to show the movies seven days a week while still trying to oversee movie production at the same time.
Meanwhile, Uncle Benjy finds he has a terminal illness. He tries to mend fences with Duddy, but Duddy rebuffs his request that the two see each other more frequently during his final days. Uncle Benjy's death acts as a trigger for Duddy, who has a nervous breakdown and refuses to leave his room for a week. Duddy loses his clients and is forced to declare bankruptcy and to surrender all his possessions to the government (except for the land, which was all in Yvette's name due to Duddy being considered a minor).
After Duddy recovers, he invites Yvette and Virgil to move with him into his uncle's mansion, which Duddy inherited on the condition that the house not be rented out or sold. When Duddy hears of the last bit of land around the lake is up for sale, he exhausts his few remaining contacts trying to raise the money he needs, but still comes up short. Pressed for time and desperate, especially knowing Dingleman has expressed interest in the land and has the money for it, Duddy forges Virgil's signature on a cheque to get the money. Yvette finds out and tells Duddy's grandfather, who is embarrassed and unhappy with the way Duddy has obtained the land. This theft also prompts Yvette and Virgil to move out of the mansion and forbid Duddy to ever see them again.
In the end, Duddy has no friend left. But back in the Montreal St. Urbain Street joint where his taxi-driving and pimping father spends most of his time, entertaining regulars with stories often involving the Boy Wonder, someone somehow recognizes Duddy as the guy who has recently acquired all of the land surrounding the lake in the Laurentians, and when Duddy, ordering servings for everyone while he has no cash left to pay for any, gestures to his father, he is answered by the patron, "That's all right, sir. We'll mark it." He has made it. He's become a "somebody". He grabs his father Max, spins him around, repeating, "you see."
