Escaping with Islamic State's secrets, he hid one of his own

He would wander the streets of occupied Mosul by day, chatting with shopkeepers and Islamic State fighters, visiting friends who worked at the hospital, swapping scraps of information. He grew out his hair and his beard and wore the shortened trousers required by the extremists. He forced himself to witness the beheadings and stonings, so he could hear killers call out the names of the condemned and their supposed crimes.