WASHINGTON — I first heard about Col. Yosef Alon, a dashing Israeli diplomat, while working as a reporter in New York almost a decade ago. Colonel Alon was fatally shot in July 1973 as he got out of a car at his home in Chevy Chase, Md., after returning from a party with his wife. The F.B.I. never solved the case.

At the time, I was curious about why the F.B.I. had not found Colonel Alon’s killers. The cold case was extraordinary: No Israeli official had ever before been assassinated in the United States. It was, at that point, the largest investigation the bureau had ever conducted.

I eventually published a lengthy article in 2007 about the F.B.I. investigation into the death of Colonel Alon, a military attaché assigned to the Israeli Embassy in Washington. It revealed new details about the C.I.A.’s belief that Palestinian terrorists had carried out the operation.

Acting on a hunch, I sent a copy to a man who might have known something about the murder: Ilich Ramírez Sánchez, the Venezuelan terrorist and Muslim convert better known as Carlos the Jackal. He was not hard to find. He was in a French prison, serving a life sentence for killing two French security agents in 1975.