Instinct or Learned?

A patient of a psychiatrist suffers recurring nightmares concerning the Oklahoma City bombing. The psychiatrist suspects that the patient is experiencing nightmares caused by another personality in his head, and this personality X is attempting to take control of the patient. The psychiatrist uses hypnosis to access X, which he does. The patient is losing his ability to fight off this personality on a daily basis. In order to eliminate X, the doctor must know more about him if possible, so the doctor also becomes a detective. In the process, the doctor discovers that the personality is a killer, which accelerates his need to eliminate this vial personality. With the aid of a specialist, the psychiatrist discovers an unlikely surgery to remove a small part of the patient brain housing the evil personality. In performing his research, the psychiatrist discovers the answer to the question of instinct or learned.