Professor Digory Kirke has called all of his "Friends of Narnia" together, including Polly Plumber, Peter, Edmund, Lucy, Eustace, and Jill, but not Susan, as she doesn't believe anymore. Digory feels that there is something bad happening in Narnia. Since Eustace and Jill were not told that they would not return to Narnia, the group devises a plan to use the rings Digory and Polly used to first enter Narnia. Peter and Edmund go to London to acquire them.
An ape, Shift, and a donkey, Puzzle, live a little ways off from a village. Shift spends his time manipulating Puzzle into doing whatever he wants (or doesn't want) to do. Just as Shift is convincing Puzzle to go to the market for him, he sees something coming down the waterfall. He sends Puzzle in after it. Puzzle pulls out a lion's skin and Shift wants to use it to dress Puzzle up as Aslan. Puzzle doesn't think it is a good idea, but Shift convinces them that they could do some real good. However, the ape instead teams up with the Rishda Tarkann, the leader of the Calormenes, to enslave the Narnians.
A centaur, Roonwit, comes to warn King Tirian that the rumors of Aslan's return are false. However, since centaurs use the stars to tell the future, King Tirian is not convinced that Aslan would allow the stars to predict his coming. He sets off with his friend, Jewel the unicorn, to find Aslan. He listens as Shift tells the Narnians that Aslan and the Calormene god, Tash, are the same. Tirian won't stand for it and announces that the ape is lying. He is overtaken by the Calormenes and tied to a tree.
The Friends of Narnia see King Tirian tied to the tree and try to talk to him. However, he cannot hear them. Shortly after, Eustace and Jill are transported to Narnia without the use of the rings. They free King Tirian, Jewel, Puzzle(who was kept in the stable when not needed to impersonate Aslan), and a group of dwarves. However, all of the dwarves but one, Poggin, are not willing to fight for anyone but themselves. They prepare for what might be their last fight.
Upon returning to the stable, they see that Shift, a cat named Ginger, and the Calormenes have devised a plan to kill the Narnians one by one. They plan to let each animal into the stable one by one to talk to Aslan. However, the real plan is to have a guard on the other side of the door that kills them after they enter. The cat is supposed to enter first, to show that no harm will come to them, but instead of the guard just letting him go, he meets Tash inside of the stable and looses the ability to speak. A righteous Calormene guard volunteers to enter the stable and the Calormenes, though they try, are unable to prevent him.
King Tirian and his forces attack. Shift is thrown into the stable and devoured by Tash. The animals are killed. The dwarves are fighting randomly, not helping either side. Eustace, Jill, and Poggin are forced into the stable. King Tirian continues to fight and eventually pulls Rishda Tarkaan into the stable with him. Digory, Polly, Peter, Edmund, and Lucy also appear in the stable. Those who believe in Aslan are able to see light and beautiful scenery, with the nonbelievers wondering in the dark. Peter orders Tash away and Aslan appears, sorting out the believers and nonbelievers. The righteous Calormene guard apologizes for his devotion to Tash, and Aslan explains to him that he was doing good and has always been serving Aslan.
Aslan leads them to his country, the real Narnia. They meet their friends from their previous adventures in Narnia. Peter, Edmund, and Lucy see their parents and are curious as to how they got there. They realize (and Aslan confirms) that there was a train crash and they all died, except Susan. This is where their real story begins.
The Chronicles of Narnia:
The Lion, The Witch, and the Wardrobe
The Voyage of the Dawn Treader
The Silver Chair
The Horse and His Boy
The Magician's Nephew
The Last Battle