The Old English Baron follows the adventurous story of Sir Philip Harclay, who, after returning to medieval England, finds that Arthur Lord Lovel, a childhood friend, is dead. He discovered that Arthur's cousin Walter Lord Lovel had inherited the estate and sold the family castle to the baron, Fitz-Owen. But things take a turn when a mysteriously abandoned set of rooms in the castle promises to reveal the secrets of the past. After a series of surprising twists and turns, the legitimacy of the true heir is finally discovered.