Following the death of her six-year-old son in a car accident, all Frances Cairnes wants is to hunt down and kill the man she believes is responsible. When she finally tracks him down, she tricks her way into his house and plots his murder from within.
Set on the Isle of Wight, The Beast Must Die follows the story of the hit and run of a young boy, whose mother, Frances (Cush Jumbo), is intent on avenging his death. This drive to get revenge keeps her going in a hunt to find and kill the man she believes was behind the wheel of the car. While she takes things into her own hands, the troubled yet brilliant Detective Strangeways (Billy Howle) has to unpick this web of tragedy and steer a course to justice.