There are no publicly available photos of Hassan Ghul, no written statements by him. Yet over the past decade, Ghul, a native of Pakistan and member of Al Qaeda, was one of the most important players in the war between the United States and its terrorist enemies. American officials say he knew the 9/11 masterminds and was a key liaison to Qaeda-linked groups in Iraq; that he was a prisoner at the CIA’s black sites, where he experienced the agency’s harsh interrogation techniques—and that the intel he divulged was crucial in helping the U.S. track and kill Osama bin Laden.

Officials with knowledge of the case say that after being treated brutally in U.S. and Pakistani custody, Ghul agreed to become a double agent and work against Bin Laden’s deadly terror network.

sources say Ghul vanished, turned triple agent and once again embraced his terrorist allies. In the end, a CIA drone strike killed him in the fall of 2012. But unraveling the tangled story of his final years shines new light on U.S. secret prisons, harsh interrogation methods, morally ambivalent spy games and America’s tortured relations with Pakistan. It’s a rare if murky window into the world of global spycraft.