Born To Run by Michael Morpurgo

When Patrick sees a wriggling bag in the canal on his way to school, so he 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 puppy he calls Best Mate, and after a debate with his parents, he is allowed to take Best Mate home. Patrick and Best Mate become like best friends 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 to become her own pet and called him Bright eyes. But then, Suzie went into danger and got split up.