For more than two decades, Robert Hanssen, a former FBI agent, spied off and on for Moscow during and after the Cold War. He spied through the terms of four presidents and three FBI directors and became one of the most damaging espionage cases in American history. Lis Wiehl, a former Federal Prosecutor, daughter of an FBI agent, and author of A Spy in Plain Sight: The Inside Story of the FBI and Robert Hanssen, joins Dan to share an inside perspective on how Hanssen fooled so many for so long.