Future Hawaii 5-0 regular James MacArthur guest-stars as Jase Fredericks, who tries to protect his inheritance, and his life, from his selfish uncle Bingham (Ford Rainey). The Cartwrights become involved when the conflict between Jase and Bingham boils down to Jase's prize stallion. Patricia Hyland costars as Jase's wife Kathy. Originally broadcast on December 3, 1967, "Check Rein" was written by Robert I. Holt and Olney Sherman. ~ Hal Erickson, Rovi