Storyline: Private detective teams up with an ex-cop to solve a kidnapping case in Montana. Big Sky is an American crime drama-thriller series created by David E. Kelley and based on the 2013 novel The Highway by C. J. Box. The series premiered on ABC as a fall entry in the 202021 television season on November 17, 2020. Private detectives Cassie Dewell and Cody Hoyt join forces with his estranged wife and ex-cop, Jenny Hoyt, to search for two sisters who have been kidnapped by a truck driver on a remote highway in Montana.