Jack Morgan is a dog therapist who once enjoyed fame for allegedly reading his dogs’ minds. Although he can’t actually read the minds of other dogs, he keeps this limitation hidden from his clients and runs a canine mind-reading business with a confident air. When Mr. Mooney and his wife bring their dog in for a session, they leave dissatisfied with Jack’s perceived limits, and Mr. Mooney—an ally of the city mayor—threatens to shut the operation down. After the Mooneys depart, a wealthy client named Clyde Windsor visits with his dog, Lucky, and Jack is astonished by how clearly he seems to understand Lucky’s thoughts. The encounter leaves him unsettled, and he ends the session early. Before Windsor leaves, Jack informs him that Lucky is troubled by three people living with him.
Two weeks pass, and the city closes Jack’s business. At the same time, Windsor’s personal driver, Calvin Bridges, informs Jack that Windsor has died. Windsor’s lawyer, Allison Kent, reads the will to Windsor’s relatives—his niece Margaret and nephews Lyle and Reuben—reveal that the trio will receive almost nothing from the estate. Windsor has chosen Lucky to inherit the fortune and the mansion. In a twist, Jack is named Windsor’s trusted fiduciary for Lucky’s $64 million trust fund, and he agrees to move into the mansion and oversee Lucky’s affairs, which effectively pushes Lyle, Margaret, and Reuben out of their expected inheritance.
The former heirs hire Mr. Phister, a striving but greedy lawyer who will take the case to trial for a hefty percentage of the estate. The relatives, accustomed to a life of luxury, plot to reclaim the mansion and try to become trustees of the trust on their own. One night, as Lucky grows excited about bones buried in the mansion’s yard, Jack starts to act like a dog himself and eventually shares in Lucky’s instincts to the point of tearing up furniture and alarming the mansion’s two maids. The next morning, Jack explains to Calvin that when Lucky becomes overly excited, he takes over Jack’s body and Jack effectively becomes Lucky.
To help Lucky cope with his owner’s death, Jack and Calvin take him to a local mall. In the mall’s pet store, Jack signs additional paperwork for Allison and meets her daughter Nicole, who dreams of a puppy; Allison, however, tells her daughter that their living situation isn’t suitable for a puppy. In the mall’s food court, Lucky’s scent-induced excitement causes Jack to transform again into Lucky, and the two share a meal by scavenging leftovers and trash, a sight that underscores their strange connection.
Facing mounting pressure, Windsor’s relatives push for a trial, and Phister’s firm offer seems tempting. At the courthouse, Jack demonstrates his bond with Lucky by inciting Lucky’s excitement and proving that when Lucky takes control, he can identify objects he cannot see. Through Lucky’s thoughts, Jack uncovers a possible motive for Windsor’s death: Lyle is accused of poisoning his uncle. Tension peaks when Lyle threatens the courtroom with a gun, but Lucky intervenes, knocking Lyle over and leading to the arrest of Lyle, Margaret, and Reuben.
Back at the mansion, Jack shocks everyone by revealing a plan that involves the dogs he has acquired from the mall’s pet store. He has arranged for a large number of dogs to live at the estate, including a puppy for Nicole and a female companion for Lucky, ensuring that Lucky won’t be alone and reinforcing Jack’s own unusual role in the mansion’s unfolding drama. The story threads together loyalty, wealth, and the enigmatic bond between a man and the dog that shares his mind.
