Aired on January 21, 1940,based on the 1937 novel by A.J. Cronin.

The Citadel follows Dr. Andrew Manson, a young and idealistic Scottish physician who begins his career in a Welsh mining town. Confronted with poor working conditions and inadequate medical facilities, Manson strives to improve public health standards. As he gains recognition, he's tempted by the allure of wealth and prestige, leading him to question his principles and the true purpose of his profession.