When police detective Mort Shade is killed in the line of duty, his partner, vice cop John Dark leaves the scene to get help. When he returns to the body he is surprised to find Mort seemingly alive and well. In the weeks that follow, some of the most notorious and untouchable criminals that the two cops are tracking turn up dead in savage attacks, the work of some sort of bestial vigilante. Dark soon discovers that his partner has undergone a physical transformation and is responsible for these unexplainable killings. With his morality tested to the very limit, will he turn in his friend and partner or will he stay silent and watch the gruesome body count grow?