Sian's investigation into a reported UFO sighting by 14 schoolboys in a playground in west Wales ramps up a gear. Now she has a tape of hotelier Rosa claiming she saw a spaceship land and two "creatures" appear weeks before the primary school sighting in Broad Haven. Whatever the truth of what Rosa saw that night, it makes her the first witness in the case. Sian heads to the hilltop Haven Fort Hotel Rosa owned to try to track her down. As Sian digs through the original case files, she hones in on rational explanations for what happened, only for new information to suggest there could be some truth to the stories. Was Rosa making the story up to drum up business for her hotel? If so, why was she genuinely terrified as the police officer who responded to her 999 call that night recalls? A new lead finds Sian reluctantly descending into an abandoned bunker near where the figures apparently appeared. She's barely processed what she finds before she learns of another theory from the time — that it was all a hoax by locals on a drunken night out. But when Sian finally tracks down Rosa's daughter, the hoax theory is blown apart. And, Sian's left reeling by fresh reports of multiple eyewitnesses seeing a strange orb of light over Stack Rocks just off the coast at the same moment. Unsettled and overwhelmed, Sian uncovers an interview in original investigator Randall's archive with one of the eyewitnesses, Pauline, who lived in the farm opposite Stack Rocks. Her account of a night-time chase with her young children in the car is the most terrifying yet.