When sisters Claire and Sophie Martinez discover a secret ladder in their great-aunt's fireplace, they're transported to the magical world of Arden. There, they learn that Arden is in grave danger—all the magic is disappearing, and legendary creatures like unicorns are missing. The sisters embark on a dangerous quest to find the last unicorn and save both Arden and their own world, discovering hidden strengths and the powerful bond of family along the way.