For Mulcahy, the only explanation was amnesia.
The phenomenon of amnesia is clouded in mystery. Why it occurs in some patients and not in others is open to medical speculation. What is known is that loss of memory can be caused by stroke, Alzheimer’s disease, alcoholism, severe psychological trauma—or by blows to the head. Any individual whose brain has suffered such injuries can simply wander aimlessly away from the place where he lives, with all knowledge of his past blacked out