In the beautiful armor Joseph Lequire has created for Moonsilver, no one can tell he is a unicorn. It's safe for Heart to travel to Bidenfast, where she hopes to find her Gypsy friends. But the streets are jammed with people in town for the crowning of the new Lord Irmaedith, and the young lord himself takes a special interest in the unicorns. Will Heart be able to keep her secret?

It has been a long, hard winter, and the Gypsies are glad to be leaving Lord Levin's mountains for the sunny plains of Lord Kaybale's lands. But that means time is running out for Heart. The old stories say that Castle Avamir is higher than the clouds, deep in a valley, under the stars, and over the moon.
It makes no sense -- but if Heart can't solve the riddle, she might never find a safe haven for her beloved unicorns.

Heart is convinced that the old man from Castle Avamir can help her find her family -- the only people she dares to trust with the Unicorn's secret. But the old man has been taken prisoner by Lord Dunraven. Heart's search for the truth is leading her into the most dangerous place of all: the depths of Dunraven's heavily guarded castle.
Heart's quest is nearing its end -- and what awaits her is beyond her wildest imaginings....