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. Still, Cat is touched by the person that lives within the Beast and she knows she has to keep her relationship with Vincent a secret from her boss, Joe Bishop, her partner, Tess Vargas, and even from her close friend, Evan Marks, the medical examiner. Cat and Vincent are powerfully drawn to one another, but they understand that their connection is extremely dangerous for both of them.