Five years went by since the founding of the Soter Herd. The last of Soter's Messengers has passed away. Now, Aurora, Soter's half-sister, her mate Midnight, their twin foals, and their zebra friend Kumani wait for the promised return of the Light Horse.

One day, a mysterious horse appears, captivating equines around the world with his magical powers. Many are convinced that the Light Horse has finally returned, but Aurora and Midnight have suspicions. And when they discover the stallion's sinister plot for world domination, they join forces with old and new friends to stop him. But there is more to the evil stallion than meets the eye. Soon, Aurora, her family, and many of the Soter Herd will witness Equus's last days... and the final, epic battle between the Light Horse and Dark Horse.