reporter: what began with fire became murder and manhunt. the level of intensity in this investigation is incredible. reporter: a best friend turned worst enemy. this gentleman was a friend of ours for a long time has taken everything. reporter: hundreds in desperate pursuit of one teen in grave danger. the amber alert was on. i see a picture of this blonde-haired girl. i said that s the girl we ve seen up on the mountain. reporter: kidnapped, the rescue of hanna anderson. it was going to be a normal summer weekend, pop warner football for ethan. cheering practice for hannah. a road trip for the dog and mom christina to jim s house.