The Shadow Patrol, Paperback

In late 2009, CIA officers in Afghanistan's Kabul station allowed a Jordanian doctor into their closest confidence. In truth, the doctor was an al-Qaeda double agent--and when he blew himself up, the station's most senior officers died with him.
Years later, the station still hasn't recovered. Recruiting has dried up and the agency's best Afghani sources are being eliminated. At Langley, the CIA's chiefs begin to suspect the worst: somehow, the Taliban has infiltrated the station.
When they ask John Wells to investigate, he reluctantly agrees to return to the country where his career began. One thing is certain: Americans are dying, and an American is responsible. Wells is the only one who can unearth the truth--if it doesn't bury him first . . .