The Wood Between the Worlds (Chronicles of Narnia)

Polly and Digory are spending the summer in London. One day, while exploring the attic, they discover a secret passage. Polly finds some magical rings, and when she and Digory put them on, they mysteriously travel out of this world. Polly and Digorys dangerous journey into new worlds and their discovery of Narnia is only the beginning of their adventure.