A human girl visits the Rainbow Realm, an enchanted land ruled by a circle of unicorn princesses, to help Princess Sunbeam regain her magical powers.

Unicorn Princess Bloom asks the human girl Cressida to help with final preparations for her birthday party, but when they discover quails destroying the party decorations and realize that the invitation to Princess Bloom's best friend has gone astray, they fear the celebration will be ruined.

Princess Breeze invites her human friend, Cressida, to attend the Blast, a festival featuring kite flying, but the wizard-lizard, Ernest, has blundered again and now giant bats sleep on the kites.

Cressida returns to the Rainbow Realm, where she helps Princess Firefly, the orange unicorn, with the opening of a new library.