Midshipman Roger Byam joins Captain Bligh and Fletcher Christian aboard the HMS Bounty for a voyage to Tahiti. Bligh proves to be a brutal tyrant and, after six pleasant months on Tahiti, Christian leads the crew to mutiny on the homeward voyage. Even though Byam takes no part in the mutiny, he must defend himself against charges that he supported Christian.
Leo Vincey, told by his dying uncle of a lost land visited 500 years ago by his ancestor, heads out with family friend Horace Holly to try to discover the land and its secret of immortality, said to be contained within a mystic fire. Picking up Tanya, a guide's daughter, in the frozen Russian arctic, they stumble upon Kor, revealed to be a hidden civilization ruled over by an immortal queen, called She, who believes Vincey is her long-lost lover John Vincey, Leo's ancestor.
Kay, a bored society girl from New York, takes a trip to Greece-where she meets, Terry, an archaeologist. Kay flirts with Terry and he falls for Kay. Kay heads back to New York and Terry follows her to propose marriage. Terry sees Kays lifestyle is uncomfortable. He decides to leave, but, Mrs. Gage (Kay's grandmother) encourages Terry to stay. They become engaged. Just before the wedding Kay and Terry have a huge quarrel. Will Terry be left at the altar?
In 1917 Lt. Bill Gordon is headed for France when he meets and becomes friendly with Joel Carter, niece of the Asst. Secretary of War. Finding out that he is an expert on codes, she gets her uncle to cancel Bill's orders and has him reassigned to break enemy codes. In his new assignment he becomes involved with beautiful Russian spy Olivia Karloff, who is working for the Germans, and must juggle Joel's affection and his pursuit of Karloff's connections to retrieve a stolen code book.