Frost and his men assist RSPCA officer Christine Moorhead in smashing an illegal dog fighting ring but its organizer, local gangster Gerry Berland, eludes them. One of Christine's helpers, Brian, is stabbed to death by Berland's thuggish son Sean, who believes he set the police on the ring,and Christine recognizes him and his accomplice,Neil. Berland arranges alibis for the boys and though initially appalled, his wife Sally colludes with him as he has always run her life. She persuades Neil's honest and horrified parents to go along with the lie. Having failed to warn Christine off, Berland sends a thug, Lisowski, to torch the RSPCA unit with Christine inside it with her rescued dogs. Meanwhile a mysterious criminal is duplicating unsolved crimes on Frost's books from years earlier and, as he goes to rescue Christine, Jack finds,chalked on his drive, 'You Die Next.'