An Old Captivity tells the story of a young pilot named Donald Ross, who is hired to fly a wealthy American archaeologist, John Mathewson, and his beautiful daughter, Jean, to a remote part of Greenland in search of Viking relics. Along the way, Ross and Jean develop a romantic relationship, and they uncover a secret about the Vikings that could rewrite history. The novel combines adventure, romance, and historical fiction to create an engaging story that explores the themes of love, loyalty, and the pursuit of knowledge.