In trying to prove that the ISI knew of Bin Laden’s whereabouts and protected him, I struggled for more than two years to piece together something other than circumstantial evidence and suppositions from sources with no direct knowledge. Only one man, a former ISI chief and retired general, Ziauddin Butt, told me that he thought Musharraf had arranged to hide Bin Laden in Abbottabad. But he had no proof and, under pressure, claimed in the Pakistani press that he’d been misunderstood. Finally, on a winter evening in 2012, I got the confirmation I was looking for. According to one inside source, the ISI actually ran a special desk assigned to handle Bin Laden. It was operated independently, led by an officer who made his own decisions and did not report to a superior. He handled only one person: Bin Laden. I was sitting at an outdoor cafe when I learned this, and I remember gasping, though quietly so as not to draw attention. (Two former senior American officials later told me that the information was consistent with their own conclusions.) This was what Afghans knew, and Taliban fighters had told me, but finally someone on the inside was admitting it. The desk was wholly deniable by virtually everyone at the ISI — such is how supersecret intelligence units operate — but the top military bosses knew about it, I was told.