Since Helms was 3-years-old at the time he originally received the letter, he lost track of it over the years.
The letter astounded the CIA museum's curatorial staff when it was acquired in May -- and not only because Helms wrote with such paternal tenderness. It also conveyed a certain historical intuition about the evil that one man could do. The letter happened to arrive at Langley the day after Osama bin Laden was killed in May.
Helms father, Richard, was one of the founding members of the CIA and rose to become the agency's director. A biographer described the elder Helms, who died in 2002, as the "gentlemanly planner of assassinations" but was eventually pushed out during the Nixon administration because, Helms believed, he didn't allow the agency to be used in the cover up of the break-in of the Democratic National Committee headquarters at the Watergate.
CLARIFICATION:This post has been updated to reflect that Richard Helms was a U.S. intelligence officer in Office of Strategic Services, the intelligence service that preceded the Central Intelligence Agency, at the time he wrote the letter to his son in 1945.