When she was a teenager, Catherine “Cat” Chandler witnessed the murder of her mother. Cat would have been killed too, but someone – or something – saved her. Now, years have passed and Cat is a police officer, investigating a case that leads her to the person who saved her: a doctor named Vincent Keller. With the help of his childhood friend J.T. Forbes, Vincent has been in hiding, guarding his secret – when enraged, he becomes a terrifying beast, unable to control his super strength.