Sandra Grimes in 2013. She had planned to retire from the C.I.A. in 1991, but stayed on to help track down a traitor / Nikki Kahn/The Washington Post, via Getty Images
Ms. Grimes was part of a small team that the C.I.A. created to investigate the disappearance of its Soviet bloc “assets,” who, beginning in 1985, were arrested, interrogated and executed for treason. Their loss wiped out a network of informants that the agency had long cultivated.
Long before the C.I.A. accepted that it had an internal leaker, Ms. Grimes, who had once car-pooled with Mr. Ames, was convinced that he was the mole.
Only after Ms. Grimes in 1992 correlated Mr. Ames’s large bank deposits to his boozy lunch meetings with a Russian official did the F.B.I. take over the case in 1993. Its investigation included sifting through Mr. Ames’s trash and tracking his car. He was arrested in February 1994.