The doctor explains that Petra's brain has had from birth a small "defect" in it. It is a tiny channel of fluid running through her skull, like a tiny vein through marble, or a small hole in an oak board, winding from front to rear. Only a CAT scan would catch it, and Petra would have never noticed it.

But in Petra's case, the shotgun buck shot, maybe even the size used for deer hunting, enters her brain from the exact point of this defect. Like a marble through a small tube, the defect channels the bullet from Petra's nose through her brain. It turns slightly several times, and comes to rest at the rear of her brain. And in the process, the bullet misses all the vital areas of the brain. In many ways, it almost misses the brain itself. Like a giant BB though a straw created in Petra's brain before she was born, it follows the route of the defect. It is channeled in the least harmful way. A millimeter in any direction and the channel is missed. The brain is destroyed. Evil wins a round.