There's only a handful of mediums worldwide who claim to do anything close to what Helen Duncan said she could and physically manifest spirits into a room. For Sian, the only way to fully understand what was happening at Helen's séances is to witness this for herself, so she tracks one of these rare mediums down in the Netherlands. Sian arrives at the Dutch monastery and is greeted by a host who takes Sian on a private tour of the séance room, where the medium will work that evening. The traditions haven't changed much since Helen's 1930s séances. The medium will be searched, then tied to a chair, enclosed behind a black curtain, and spirits, depending on what unfolds that night, may physically 'appear'. The room will be pitch black, and Sian will be locked inside. Sian is left visibly shaken after attending the séance. But the next morning, having had time to give thought to all she heard and saw, she takes the opportunity to confront the medium and ask all of her questions, including putting to him whether there is deception involved. Back in the UK, and chasing a previous lead, Sian reads an astonishing account of Helen bringing back a WWII sailor from the dead in Portsmouth. He "appears" in the uniform of the warship HMS Barham and reveals the ship has gone down. Crucially, this information of HMS Barham's sinking was a state secret at the time. Sian digs deeper into how Helen could have got hold of the information and is disturbed by one theory that she could have been using deception in wartime, when so many were experiencing grief and desperate for comfort. But a fresh lead opens up a whole new line of inquiry, when Sian discovers a recently declassified diary of a director of MI5. Her investigation escalates to new heights when this diary reveals MI5 was tracking Helen.