The villainous King Haggard plots to destroy all the Earth's unicorns. When a young unicorn named Amalthea learns from a butterfly that her forest in danger and that she may soon be the last of her kind, she leaves the safety of her protected forest and enlists the help of Schmendrick, a gentle, albeit clumsy, sorcerer. Together with a middle aged maid named Molly Grue, they embark on a long and dangerous journey with one goal: to defeat Haggard and save the unicorns from extinction.