While walking in the forest of his little kingdom, a little king sees an extraordinary being white as snow, fast as the wind and with a horn on his forehead. Unfortunately, the creature immediately disappears, and despite the help of the knight Petitpas, it remains nowhere to be found. Only the little queen, tender and gentle, will succeed in meeting the mythical animal and bringing it back to the little castle. The little king is delighted, the little queen takes care of her guest but, strangely, the unicorn spends his days and nights at the window.