Right now, Australians love betting on greyhound racing, the sport based on pushing dogs to their limits. With more than 40,000 races and more than 300,000 dogs running at tracks across the country each year, Australians are now wagering $4 billion a year on the sport. Prize-money has skyrocketed and greyhound racing is riding a wave of renewed popularity.

The message to punters is that the sport has cleaned-up and modernised; the welfare of animals is now at the forefront of the industry. But things are not as they seem. This week Four Corners reporter Caro Meldrum-Hanna leads a gritty investigation into the darkest secrets of the sport, exposing the gruesome underbelly of greyhound racing. This investigation will rock the industry, and the sport, to its core.