Cotton plays Sam Flusky, a native Briton banished to Australia for murder. Bergman is his wife, Henrietta, the disturbed sister of the man Flusky was convicted of killing. When a new governor arrives, he brings with him his cousin Adare, an old friend of Henrietta's, who sets out to help her conquer her demons and return her life to normal, but there are complications. Is Henrietta going insane, or is someone trying to drive her mad? Is she merely an alcoholic, or is someone trying to poison her? Under Capricorn is a lush technicolor melodrama.