One night when Ludo is home alone, his family's only horse, Renti, escapes from the stable. Overcome with guilt and fear, Ludo follows Renti out in to the snow, and before long the pair find themselves in the House of the Archer, a gateway to the Zodiac. Here, the Archer tells Ludo that Renti is a Star Horse, and has chosen to return to his own kind. Ludo, says the Archer, may keep faith with Renti and accompany him, or, if he prefers, return home. Ludo decides that he must repay Renti's years of loyal service, and so the pair set off on a journey through the houses of the zodiac, or 'Star Countries'. They must pass through all twelve before catching the sun - but Ludo soon realises that many of the house rulers are less than hospitable. Dismissed by the imperious goat, chased by the crab, taunted by the bloodthirsty twins... theirs is a perilous and unpredictable journey...