The Secret Rescuers: The Sky Unicorn by Paula Harrison

When Clover, a baby sky unicorn is taken from his herd by Sir Fitzroy, a knight determined to destroy all magical creatures, young Ava devises a plan to rescue the foal.  Wearing a disguise, Ava sets out under cover of night to find Clover.  The young unicorn must be able to fly, and fly quickly, if the rescue plan is to work, but Clover has not learned how to even lift off the ground.  Fantasy and fairy-tale lovers 6+ won't be able to put down this illustrated tale.