When Patrick sees a wriggling bag in the canal on his way to school, something compels him to jump in and retrieve it. Inside is a litter of greyhound puppies, cruelly left to drown. He falls in love with the littlest one, a beautiful fawn puppy he calls Best Mate, and after a protracted battle with his parents, he is allowed to take Best Mate home. Patrick and Best Mate become inseparable until one day the dog is stolen by a greyhound trainer, where he begins a new life as a racing champion. This life though, is not so good. The trainer is cruel and once his dogs are past their best, once they stop winning, they disappear, never to be seen again. Suzie, the trainer's step-daughter, doesn't believe for a moment that they are being sent to a happy retirement. And when she sees their true fate with her own eyes, she resolves to save Best Mate from an inevitable and gruesome fate.