When all the animals of Westlands are poisoned, Prism, the youngest unicorn, is sent by the goddess to find the cause. Despite her golden wings, Prism is unable to fly so makes the long treacherous journey across the mountains on foot, accompanied by Delsin, a spirit man and Rocky, a mortal horse. Prism confronts the guardian of Westlands which causes a battle between the three generations of unicorns, resulting in devastating fire and floods. Prism must find a way to warn all the inhabitants of the land to seek safety, find a cure for the plague, and discover what, or who, is behind the devastation before the whole of Equinora becomes a desolate wasteland.