After years apart, Jonathan and Samantha are reunited at last, but their dealings with the elusive Mrs. Chen have not come to an end. Cassie is now in her custody, her future uncertain as Samantha tries to adjust to a new life in the twenty-fourth century. To make matters worse, Jonathan begins to show signs of a dreaded degenerative mental condition known as Cerefugi's Syndrome. His only hope is to check into a mysterious medical facility known only as "The Library," but he refuses, knowing it will leave Sam alone in a strange world with no guarantee he can ever be cured. As the disease progresses, Samantha takes matters into her own hands, starting a chain of events that could lead to their salvation, or total destruction.