One day the last unicorn on earth is missing her lost companions and sets off on a quest to King Haggard’s castle, the dark fortress, where many moons ago the Red Bull, a giant bull-shaped fire creature, has driven the unicorns. On her dangerous journey through the world of humans and legends she soon gets caught by the witch Mommy Fortuna and displayed in the Midnight Carnival, a menagerie of mythological monsters. With the help of Schmendrick, a clueless but well-meaning magician, she gets free and releases the other creatures. One of the monsters, the Harpy, an ancient evil bird goddess, destroys Fortuna and her show. From now on Schmendrick and the unicorn are travel companions. The miserable young wizard, who hopes to become one day a true magician, will become a good friend. But for now he produces just series of funny errors. Soon he ends up in trouble and is captured by a gang of hopeless outlaws who dream to be Robin Hood. Cully, their captain, a miserable would-be-poet, welcomes the captive as his new audience. Schmendrick meets Molly here, Cully’s unhappy outlaw bride and soon their next  uninvited travel companion, and tries to impress her with his magic. Unexpectedly, the magic works for once - suddenly the ghosts of Robin Hood appear and Cully’s men leave their unfortunate captain and follow the ghosts. After more magical mishaps with a tree woman, who falls in love with Schmendrick, they continue their quest – and Molly stays with them on their journey. She knows the way better than Schmendrick...

After an exhausting journey through a deserted, dangerous land they arrive at Hagsgate, the town before King Haggard’s castle, where the town folk try to draw them into a plot against Haggard’s stepson, Prince Lir. They fear a curse on Hagsgate that was once spelled out by a witch who wasn’t paid. The same night the Red Bull scents the last unicorn in a dead forest near the fortress and hunts her down. In the last second Schmendrick lets go of his own personal, limited power. calls on the source of magic itself and turns the unicorn into a beautiful, fairy-like young woman. In this shape the Bull can’t recognize the unicorn anymore. They enter King Haggard’s court in disguise and stay there - for ages, it seems. Time seems to stand still in Haggard’s strange, half ruined, labyrinthic castle. They are trapped in a fortress that keeps altering its shape - almost a creature itself with own moodswings reflected in architecture. As the seasons go by the Lady Amalthea (formerly the unicorn) falls in love with Prince Lir, a foundling with unknown parents, adopted as a baby by the lonely tyrant king. And as their love grows, Amalthea loses her memory. Lir tries to master all heroic deeds he can think of and fights victoriously against dragons, ogres, black nights and simply any monster he can find. But the Lady Amalthea cannot be impressed by bloody acts of  heroism. Only Lir's true love and clumy poetry will open her heart at the end. But as longer she stays in her human body as more she loses her memory and begins to forget, what she came here for.

After magical encounters with a talking cat, with gargoyles and a drunk skull they finally discover the secret of the unicorns. Haggard has captured them all with the help of the Red Bull, who guards them in the sea where Haggard watches them during the tide for his private delight. Our friends finally manage to escape through a magical dragon-shaped clock into another dimension beyond time – and Lir finds them even there guided by his heart. He is determined to help Amalthea to finish her mission and free the unicorns, even if she has to turn back into a unicorn again. But their escape route through the caverns underneath the castle leads them through the lair of the Red Bull. And the beast is alert...

In a dramatic chase they reach the beach, closely followed by the Bull - no chance for any escape. And once more Schmendrick summons the power of magic successfully – and turns Amalthea back into the unicorn she was before. Prince Lir dies in a final attempt to fight the monster. In the face of her dead lover the unicorn turns around, faces her enemy and fights back. Surprise. The Red Bull, not used to magical resistance, gives way and leaves forever into the sea. 

Sunrise – giant, glittering waves - thousands of unicorns arise in mighty waves from the ocean, forming themselves into shapes out of the sea spray. The unicorns are back on earth and run free again... Haggard’s dark fortress collapses with himself and vanishes completely. In a final farewell the last unicorn touches the dead prince with her horn and brings him back to life, before she leaves forever to her magical forest – back into her eternal spring. Lir will be king now and Schmendrick has found his true power, he and Molly will stay together. Yet the last unicorn will always remember the time when she was human, when she learned what regret means – and love...