The police and social services were baffled when an elderly man with an American accent was found lost on the streets of Hereford. He didn't know who he was or have any ID, and he was dressed from head to toe in brand new clothes from Tesco. He was in a nursing home before Panorama took up his case. Reporter Darragh Macintyre follows the clues to America and unravels the mystery of the unknown man - before confronting the person responsible for bringing him to Britain.