Willie Joy cleans the greyhound track, a job that keeps him on his feet between races as he scrapes up dog droppings and keeps the place running. One day, a trap is sprung on him: he’s lured into standing in the path of the mechanical lure, and when the lure shoots past with the dogs in hot pursuit, he loses his balance and tumbles onto the moving line. The incident costs him his job, and he’s fired for the mishap.
Breeder Bert Benton arrives with a sick dog and sells it to Joy, who takes the animal home only to be faced with eviction from his landlady. In short order, he crosses paths with a smooth-talking con man, Captain Jack Montague, and the two hatch a get-rich-quick scheme around the dog, whom they christen Lindy Lou. As Lindy Lou is nursed back to health, she begins showing promise in racing trials, drawing Benton’s interest for a possible buyback that would endanger Joy’s fragile new setup.
Behind the scenes, crooks exploit Joy as an unwitting accomplice in race fixing, arranging large bets while manipulating the outcomes for profit. The plan involves passing doped meat to the dog, although Joy and Montague end up consuming it themselves in a moment of miscalculation and guilt. The criminals discover Joy and Montague asleep, and a desperate bid unfolds as they can’t locate Lindy Lou. In a tense sabotage move, they detach Montague’s railway carriage home and cart it onto an active rail line, hoping to derail their enemies. The crew awakens with a grim realization: they’re near Doncaster, and Lindy Lou is saved from disaster just in time as the carriage narrowly avoids a catastrophic crash.
In the climactic moments, Lindy Lou captivates the crowd and wins the Gold Cup, a victory earned more through timing and distraction than raw speed, while Joy’s reckless whimsy backfires into a confrontation with law enforcement. He assaults a policeman to ensure a whistle is blown, exposing the ringleader of the crooks as the trail leads to Haines of Scotland Yard. The outcome seals Joy’s arrest, but Lindy Lou’s triumph lingers as the standout moment of the race night, a hard-earned prize born from a tangled web of deceit, risk, and a dog’s undeniable instinct to run.
