Gwenaella lives in France at a time when unicorns and mermaids are believed to exist, but she's never seen any. She's in a convent school being taught by nuns so that she will marry a rich merchant someday. But she has a secret admirer, Guillame, a mere scholar. Then her brother is taken ill and her father summons her home to help nurse him, telling her that it is a mermaid's curse. Gwen knows that a unicorn can cure any illness, so she bravely sets out to the nearby forest where they are rumoured to live, and puts herself in the debt of a sorceress as well as the unicorns.

THE GARDEN AT THE ROOF OF THE WORLD is home to the Tree of Life and the sorceress tells Gwen that fruit from that tree is needed to help restore the eldest unicorn. This will be a dangerous journey but a unicorn mare will travel with her and other girls will be selected as companions. Adele is one such girl; the illegitimate daughter of a baron, she lives by her wits and flees the city dressed as a pilgrim when the baron's enemies send soldiers after her. Elise is wealthy but there is a rumour that the ladies of Poitiers are unchaste, and she is rejected as a possible bride. The only way she can think of to prove her virtue is to touch a unicorn in front of witnesses. But sneaking out is a bad idea, as some knights feel they can demand anything of a girl dressed as a peasant, and her quest is almost ended before it begins.

I found this detailed, sometimes amusing tale is reminiscent of Pilgrim's Progress as the three girls meet and travel with one accord. Demons, wolves, ogres and bandits lurk in the woods and the unicorn mare is not enough to protect them; they have to protect themselves. A city, even one such as Paris with paved streets, is equally dangerous to girls. The mermaid's curse returns to haunt Gwen when she takes ship. The travels take them to cities such as Antioch and across India, giving them the chance to meet people of other cultures in contrast to the Crusades in progress, and some young men decide to take up their quest.

Fantasy fans will enjoy this mix of European and Sanskrit folk tales with rich invention and travel lore. The author WBJ Williams lives in Boston and enjoys history and anthropology, and in THE GARDEN AT THE ROOF OF THE WORLD has created a mystic and stirring blend of thirteenth- century cultures.