On Mary Rose's eighteenth birthday, her grandmother asks her to fulfill her last wish: to return the fortune of the unicorn. It is a big task, it is a great journey, it is an honour and a burden. Mary Rose must not fail to complete this mission. At stake is everything her grandmother believes in - and everything she herself believes in. It takes all her courage, but she gets on her horse and travels from Scotland across Great Britain and Europe towards her destination. Yet, Mary Rose has no idea that this mission will turn her into a knight of the unicorn, nor that she will find what she had been looking for: her purpose.
At the same time in a far away land, in the Austrian Alps, another young woman called Rosmarie is struggling with her own eighteenth birthday. She has always had the feeling, that something is missing. Suddenly, a family secret is revealed that changes everything in the eyes of Rosmarie. She wants to find out everything about the mysterious white horse, the witch who once lived in the forest and the unicorn which is the family's emblem. In the course of her inquiry she stumbles across broken pieces of the past. But the family puzzle is more complex than she thought. Will she solve it?
Whilst Mary Rose needs all her strength to keep going, despite all the challenges on her way, Rosmarie is diving deeper and deeper into her family's secret history. Little do they know that they both will find the answers to their questions only when their paths cross.