Daniel Keyes, a longtime student of psychopathology, spent many hours in psychiatric hospitals with specialists working with patients with rare disorders. The result was his novels that detail the most fragile, most unpredictable, and most fascinating mechanism—the human psyche.

'The Fifth Sally,' written two years before the famous 'The Mysterious Case of Billy Milligan,' tells the story of Sally Porter, a waitress at a New York restaurant. At first glance, she is an ordinary, unremarkable woman.

But, unknown to Sally, four more women are hiding within her. Nola, a cold, intellectual artist; Derry, a cheerful daredevil; Bella, a sexually obsessed failed actress and singer; and, finally, Jinx, a potential killer filled with anger and hatred. Whenever Sally Porter finds herself in a difficult situation, she experiences a severe headache and faints. That's when one of her alters appears. If a handsome man appears, Bella flutters onto the scene. If a problem requiring intellectual effort needs to be solved, Nola takes up the matter. And if a rapist needs to be confronted, the ruthless Jinx inevitably intervenes. Psychiatrist Roger Ash faces a difficult task: by fusing four different personalities, he creates a 'fifth Sally.'