The Horse and His Boy is set during the reign of Peter, Susan, Edmund and Lucy in Narnia, the only extended story told of that period.
This book is about finding one's home. The talking horses Bree and Hwin seek their home in the land of Narnia where they were born. For Shasta and Aravis, the two humans who journey with them, finding home is more a matter of the heart.
Aslan's influence throughout "The Horse and his Boy" is at first hidden from the characters. Secretly, he delivered the infant Prince Cor of Archenland from his enemies, placing him in the hands of a Calormene fisherman (who called him Shasta). When Shasta meets Bree, it is Aslan, disguised as a "witless" lion, who drives them to join Aravis and Hwin. In the form of a cat Aslan comforts Shasta when he feels abandoned at the Tombs of the Ancient Kings (although as a lion, Aslan defends him from predatory jackals). It is Aslan who chases Bree and Hwin so that they will reach Archenland in time to warn the king of the impending attack by the Calormene army, led by Rabadash. Aslan gives Shasta the resolve to help save Archenland and Narnia from the invaders. He slashes Aravis across the back with his claws as punishment for disregarding her servant's safety when she ran away from home: the cuts on her back equal the severity of her servant's whipping.
Eventually Aslan shows himself directly to the travellers, addressing their fears, or their self-pity, or their condescension towards others, or their pomposity. After the victory over the Calormenes, Aslan reveals himself to Rabadash in an effort to free him of his arrogant and violent ways. When kind words and forgiveness fail to soften Rabadash, who calls Aslan the "demon of Narnia", Aslan resorts to an act of severe kindness: he turns Rabadash into a donkey. To cure himself of this "condition", Rabadash must present himself at the temple of the Calormene god Tash in Tashban, where in the sight of his people he would be restored to human form. But if he thereafter leaves Tashban, he would be turned back into a donkey permanently.
