After many adventures and a few heartbreaks, Tanaquil returns home to her mother's fortress in the desert only to find that everything has changed. Tanaquil's mother has fallen in love and, if she spent little time with Tanaquil before, she spends none with her now. Tanaquil is considering moving on when adventure comes for her in the shape of a red unicorn...
The red unicorn leads Tanaquil into a world that mirrors her own. Everyone she knows and loves is in this world...even she is here in the form of a princess named Tanakil. But everything here is opposite. The sky is green, wolves eat nuts, and everyone that is evil in Tanaquil's world is good here... and vice versa.
Can Tanaquil stop her evil twin Tanakil before she does the unthinkable and murders her own sister? And will Tanaquil ever be able to return to her own world? And, more importantly, if she does, will Tanaquil have the courage to tell her half-sister the awful truth...that Tanaquil is in love with her half-sister's future husband? How could such a tangled story have a happy ending...you may be surprised.
This is the last book in the trilogy that also contains Black Unicorn and Red Unicorn. All three books are wonderful, but this one is by far the best. I highly recommend them all.