The Silver Chair by C.S. Lewis

Jill Pole is crying behind the school gym after being bullied when Eustace Scrubb (a decent boy despite the unfortunate name) comes around the corner and finds her. Trying to cheer her up, he tells her about Narnia, a magical land he had visited recently with his cousins Lucy and Edmund, and how they could possibly go there if they called out to Aslan for permission. Just then, the bullies come looking for them and Eustace and Jill rush off into the bushes toward an old stone wall at the back of the school property.

Once they get to the wall and find a door in it open, their real adventure begins. Aslan needs their help rescuing a prince who has mysteriously disappeared. The only clue the Narnians have, is that there is a dangerous green snake somehow involved. Jill Pole (after an unfortunate incident on the edge of a cliff where she and Eustace are separated) is given four signs to look for. 1. That Eustace speak to the first person he sees when he arrives in Narnia, for that person will be an old friend. 2. That they journey north out of Narnia until they find the ruined city of the ancient giants. 3. They will find writing on a stone in that ancient city, and they must do what the writing says. 4. The first person on their adventure who asks them to do something in Aslan's name, they must obey. The two children, with the help of Puddleglum, a marshwiggle, set off toward the north, encountering obstacles and distractions along the way. Will they succeed in rescuing the missing prince? Read The Silver Chair by C.S. Lewis and find out!