Digital Card: Get instant access in the Yoto App when you buy this digital card. Play it anywhere using the app or link it to a Make Your Own Card for your kids to enjoy whenever they like.
Find out more about digital Yoto Cards, here.
Cassie's older brother Byron has fallen in with the wrong crowd; boys who are wild, reckless, and not even human at all. They are 'tylwyth teg' - Fair Folk - who tempt humans down into the dark places of the world.
And Byron is tempted. When he goes missing, Cassie and her cousin Sian follow his trail into Annwn, the underworld. Here they find that the tylwyth teg are restless - and angry. Their leader Gwenhidw wants to protect Annwn from the damage humans are doing to the world, and Byron is part of her plan. Can Cassie rescue him before it's too late?