i just wanted them down. i wanted them down right then. i was terrified. >> for sandra mcneil, that day would be the longest of her life. >> i was just going on adrenaline. it was kind of makes your heart sick to see your boys up there. >> what unlikely turn of events would draw two boys to this terrible brink? the answer has everything to do with the special bond they share. 10-year-old john has autism. his brother james, 17, is devoted to his little brother. >> he was his brother's keeper. because he loves his brother, because he had been put in a position to watch out for his brother his whole life. >> part of caring for john means keeping him out of trouble. >> he has no fear of danger.