Perfect love casts out fear. Celestia home to the Legion of the Unicorn is a remarkable place where the power of love prevails over fear. Nick and Bethany immortal humans are unicorn riders. Along with other legion members they and their unicorns Lazari and Shema rescue and protect animals on earth that are in danger.After many successful trips to earth Nick and Bethany must face a crisis closer to home. The evil unicorn Hasbadana has captured Nicks sisters. Urijah the Lord of Celestia sends Nick and Bethany to confront Hasbadana and bring the sisters home. Instead Nick and Bethany are themselves imprisoned in a swirling mist of darkness deep within the crumbling stone walls of Hasbadanas castle.When Urijah willingly sacrifices himself to take the place of the humans Nick is determined to find a way to free Urijah. He seeks the advice of Animara the patriarch of the fairies. It will take the combined efforts of the Legion of the Unicorn and a new partnership with the animals of the Underground Kingdom to execute Animaras unconventional plan. Even then they dont know if it will succeed.