For the filly Estrella, nothing is more precious than freedom. She was born at sea, chattel to men sailing to the New World in search of gold. But Estrella and her herd escaped the conquerors and embarked on a journey across thousands of miles -- braving harsh terrains and fierce predators -- to a land where they can finally run wild.

But now, an unforeseen danger threatens to destroy the pack. A boy with a special gift is lost in the wilderness, and only the horses can keep him alive. But to save the boy, the herd will have to abandon their quest, and risk galloping straight back into the hands-and harnesses- of their captors.

And so, it's up to Estrella, the herd's unlikely leader, to make a life-changing decision. Should the horses accept the orphan boy as one of their own? How do you choose between freedom and friendship?