The Sky Unicorn (The Secret Rescuers, Bk. 2)

Ava is horrified when Clover, a baby unicorn, is stolen from his herd by the evil Sir Fitzroy. She comes up with a secret plan to rescue him, and, wearing a clever disguise, Ava bravely sets off into the night. But will she be able to teach Clover to fly in time to escape?