Amelia Shepherd (narration): There are 100 billion neurons in the human brain making and re-making connections. Helping us with math. Remembering our keys, our dad's voice. Working hard all the time. So when the brain is faulty, it's a big re-wiring job and there's no margin for error. When you're going into surgery, you worry you won't wake up. But with brain surgery, you worry you will wake up but you won't be there when you do. The trouble with crossed wires is you don't know they happened until it's too late. So we have to be very careful with our connections. They take time, care, and attention. They take vigilance and single-mindedness. We re-connect everything we can as carefully as we can. And then we just have to pray to God that we got it right.