Whilst celebrating Lleu's 18th birthday, Lleu and two friends go for a boat ride, when they discover beneath the water the golden doorway to the Mabinogi (the Otherworld). They swim down and are transported back in time many centuries to the Mabinogi. There they encounter some problems with mediaeval life, and they have to deal with the conflict between fate personal choice and magic.—Jackzen
On his eighteenth birthday, Lleu's world is shaken by the news that he is adopted. On the same day, his friend Rhiannon thinks that she may be pregnant, and Dan, who lives in his big brother's shadow, is as scatty as ever.
They all put their problems aside for the day when they come together to celebrate Lleu's birthday. Venturing on a boat trip along the coast they suddenly see a change in the water. They realise that, on May Eve, they have found the golden doorway to the Otherworld, which can be seen shining deep beneath the waters.
Being an independent and stubborn girl, Rhiannon doesn't think twice before plunging into the sea, and the other two are not far behind. As they swim deeper and deeper and get closer and closer to the golden gate, they are transported many centuries ago to the incredible world of the Mabinogi.
But Rhiannon, Manawydan and Lleu Llaw Gyffes have their own mediaeval problems. Rhiannon is being forced to marry someone she doesn't love, Manawydan is trying to make things right after his brother's malicious scheming, and Lleu is trying to come to terms with his mother's rejection.
While trying to overcome these problems, the characters have to deal with the conflict between fate, personal choice and magic.
