S12, E1: When a jogger stumbles across a woman and her dog who have been brutally attacked and killed in the park, the detectives are called to the scene and determine that the victims were mauled by an animal, possibly another dog. Although they search the park with no luck, they are determined to find the dog, and hold its owner responsible for the deaths. But it is tough to track down the animal, until another innocent victim is attacked. They find the dog, a pit bull, and are finally able to sedate and capture it. The dog has a chip implanted in its ear, which allows them to trace it to a breeding farm. But the breeder says he sold the dog to a company in Brooklyn, along with several others. They find a warehouse where dogs have been tortured and "bred" for fighting, but now all the dogs are dead. Someone has drugged them all.