The Unicorn (Fairy Realm #6) by Emily Rodda

The Fairy Realm and the human
world are both in great danger!

The wicked Outland creatures are
planning an attack, and Jessie can 
only save one of her two worlds. So she
must make a terrible decision -- unless
she can convince the secretive and
powerful unicorns to help her ...

The Unicorn is Jessie's sixth 
adventure in Emily Rodda's magical
Fairy Realm series -- collect them all!