In a mystical forest, a unicorn learns from a passing butterfly that she is the last of her kind and that all others have been taken by a fearsome creature known as the Red Bull. Determined to uncover the truth, she begins a perilous journey out of her forest to discover what happened to her fellow unicorns. Along the way, she encounters various characters including Schmendrick, a bumbling but kind-hearted magician, and Molly Grue, a former maiden who becomes her loyal companion. As they traverse through dangerous lands, they face numerous challenges and dark forces intent on thwarting their quest.

Eventually, their journey leads them to the kingdom ruled by the cruel King Haggard, where the secret of the missing unicorns is hidden. In order to penetrate the king's fortress and confront the Red Bull, vital transformations and cunning strategies are required. During this journey, themes of loss, identity, and courage are explored, as each character must confront their own fears and limitations while striving to achieve their goals. The story unfolds through a blend of lyrical storytelling and evocative animation, drawing the audience into a rich tapestry of adventure and wonder.