Sian Eleri delves into reports of the biggest mass UFO sighting in Britain. Her first mission is to track down the schoolboys whose 'alien' encounter in west Wales triggered it all.

Reeling from Rosa’s account of being woken by a bright light and seeing creatures', Sian heads to Rosa’s hilltop hotel, where she claimed they 'landed' to find her.

Sian’s mind is blown to discover reports of hundreds of UFO sightings across south Wales. Could they all have imagined seeing the same object in the sky?

Sian dives deeper than ever as her investigation concludes. Will eyewitness accounts and recently unclassified documents deliver a rational explanation or something more sinister?