Two of the most notable figures from the Middle Ages–the volatile, brilliant Abelard and the equally brilliant Heloise–became the parents of their son Astralabe before Abelard’s infamous, brutal castration. The couple spent the rest of their lives as monastics, in each other’s orbits if not in shared presence, as they became movers in the glittering monastic world of the early twelfth-century France. What happened to their strangely named Astralabe? Astralabe: The Life and Times of the Son of Heloise and Abelard rescues the “lost son” from footnotes and fiction and attempts to tell instead the story of a real man living in Europe in the twelfth century. This book assembles the references to Astralabe, provides background in the history of France and Switzerland, uncovers Abelard’s relationships with his family, with the ruling house of Brittany and more, and most importantly draws together all that is known of Astralabe.