A mad gallop on a mysterious white horse takes Colum back through time and into the greatest adventure of his life. In a land of unicorns and dragons he meets the mighty Oisin of history. Could this place be the legendary Tir na nOg, Land of Eternal Youth?

Oisin decides to return to Erin with Colum to visit Finn and the Fianna. It is a journey beset by terrible dangers, the evils of the Shadowlands and a ressurected demon.

And over it all hangs the awful knowledge of what faces Oisin back in his native land ...