Gwyn's family has not been happy since the night Gwyn's sister Bethan disappeared on the Welsh mountain where they live. On his ninth birthday, Gwyn's strange granny, Nain, gives him a tin whistle, some seaweed, a brooch, a broken toy horse and a yellow scarf. She tells him to give all of them, except the horse, to the wind to see if he has inherited the magic in his family.
Captivated by Nain's words, Gwyn run out on to the mountain and lets the wind grab the brooch, his whistle as well and gives him a magical pipe through which he can hear the sounds of this strange land. The wind takes the seaweed and Gwyn sees a magical ship flying through the sky, a ship from Welsh folklore. Finally the wind takes the scarf and, next day, a strange girl turns up at school. Gwyn invites her home, and with his father recognises Bethan in her, only a paler version of Bethan.
Now only the horse is left. Nain has warned him not to use the strange figure, but after a right Gwyn takes the horse outside, the wind snatches and a horrific storm erupts. Gwyn has released the demon inside the horse and Nain tries to recapture it, but only Gwyn and Arianwen together have the strength to regain the broken horse.