Silver Chair

We've got to go north, said Edmund, and reach the ruins of a giant city. Prince Rilian, Caspian's beloved son, has mysteriously disappeared, and Jill and Eustac... » 

We've got to go north, said Edmund, and reach the ruins of a giant city. Prince Rilian, Caspian's beloved son, has mysteriously disappeared, and Jill and Eustace are brought into Narnia by Aslan to find him. However, an evil enchantress has dire plans for the prince, and for Narnia itself. «