The stories of sleeper agents are fascinating;
Jack Barsky: The KGB spy who lived the American dream
It's no secret that the Russians have long tried to plant "sleeper agents" in the US - men and women indistinguishable from normal Americans, who live - on the surface - completely normal lives. But what happens when one of them doesn't want to go home?
Jack Barsky died in September 1955, at the age of 10, and was buried in the Mount Lebanon Cemetery in the suburbs of Washington DC.
His name is on the passport of the man sitting before me now - a youthful 67-year-old East German, born Albert Dittrich. The passport is not a fake. Albert Dittrich is Jack Barsky in the eyes of the US government.
The story of how this came to be is, by Barsky's own admission, "implausible" and "ridiculous", even by the standards of Cold War espionage. But as he explains in a new memoir, Deep Undercover, it has been thoroughly checked out by the FBI. As far as anyone can tell, it is all true.