Drama-documentary telling the story of a covert British intelligence operation to eavesdrop on the conversations of 10,000 German PoWs held in three stately homes rigged with recording devices. Having been kept secret for decades before being declassified, the officers' unguarded reminiscences and confessions are read by a cast of actors including Nicholas Farrell, Rupert Frazer and Peter Harding, revealing some of the worst horrors of the Second World War.