Before Sandra Grimes became a mole hunter, she'd been ready to scale back. "I was not old enough at the time to retire," Grimes said in an interview for the National Security Archive at George Washington University, "but I was satisfied professionally. I had a family that I wanted to spend more time with."

It was 1991. Sandra Grimes had spent more than two decades with the CIA. But she agreed to stay on to help a colleague investigate why the agency's informants in the Soviet Union had "gone dark," as they say in spycraft, in 1985 and 1986. They learned they had been identified, interrogated, and often executed.

"It was a terrible, terrible reminder of the seriousness of what we did for a living," Sandra Grimes said in that National Security Archive interview. "We owed all these people who had made the sacrifice."

Their investigation led them to look closely at Aldrich Ames, whom they knew as "Rick." He was the CIA's counterintelligence chief for Soviet operations, and knew about all of the agency's informants in the USSR.

Rick Ames had episodes of public drunkenness, carried on affairs, which triggered an expensive divorce, and married one of his old informants. He started wearing tailored suits, had his teeth capped, then paid cash for a new house and bought a Jaguar. All on a civil servant's salary.

Sandra Grimes scrutinized activity logs and financial statements and noticed that three times after Ames had lunch with a Soviet embassy official in Washington, D.C., he deposited thousands into his bank account.

"Well, three matches don't make a conviction, but in my mind, Rick was the spy," Sandra Grimes recollected. "It didn't take a rocket scientist to add one plus one plus one."

Aldrich Ames was arrested in 1994 and pled guilty to espionage, after taking millions of dollars for his spy work for the Soviet Union. He is still serving a life sentence.

Sandra Grimes died on July 25 at the age of 79. Her work was crucial in catching and stopping a Soviet agent who, the Senate Intelligence Committee said, "caused more damage to the national security of the United States than any spy in the history of the CIA."

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