Karen Marshall’s body, mind, and heart do not belong to her alone. She shares them with Rosalee, a smart and perky teenager; Timee, a flamboyant, puerile youth, who wears women’s clothing; an old lady, a habitué of museums; and a dozen of others. Karen’s official diagnosis is Dissociative Identity Disorder (DID). Through personal stories, “Busy Inside” delves deeply into DID — a condition that fascinates and puzzles modern psychiatry.