Gene therapy. 20 years after the first trial, Quentin asks whether it will eventually make it into conventional medicine, and why it's taking so long. Forensic archaeology in the search for the 'disappeared' from Northern Ireland's troubles. Last weekend, Charlie Armstrong, a victim of the IRA, was at last given a proper burial. John McIlwaine explains how geophysics helped trace his hidden remains. And British geology in your pocket. To mark its 175th anniversary, the British Geological Survey crams its entire geological map of the British Isles into a smartphone app for all to use. Producer: Roland Pease.