To his friends and neighbors, Glenn L. Carle was a wholesome, stereotypical New England Yankee, a former athlete struggling against incipient middle age, someone always with his nose in an abstruse book. But for two decades Carle broke laws, stole, and lied on a daily basis about nearly everything. "I was almost never who I said I was, or did what I claimed to be doing." He was a CIA spy. He thrived in an environment of duplicity and ambiguity, flourishing in the gray areas of policy.

The Interrogator is the story of Carle's most serious assignment, when he was surged to become an...