When a dog and a police officer are injured together on the job, a life-saving surgery changes the course of history. Half dog, half man, Dog Man is sworn to protect and serve as he doggedly pursues his arch-nemesis: the feline supervillain Petey the Cat. But the rivalry between Dog Man and Petey is upended by the arrival of an adorable kitten clone of Petey, Lil Petey.