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When the Pevensie children go to Narnia for the second time it is as if King Arthur had come back to England today. This story takes place a year after the children had gone to Narnia the first time, but they find that hundreds of years had passed in Narnian time. During that time Narnia had been conquered by a people called the Telmarines and all of the old Narnian creatures had died or had been in hiding for years.
The story actually begins with one of the Telamrine rulers, Caspian, who was only a child and had been usurped from his throne by his evil Uncle Miraz. As Caspian flees for his life, he finds the Old Narnians in their hiding place. They rally around him when he promises to create a Narnia for both men and beasts, forming an army to attack Miraz. Failing their initial attacks miserably, they blow a magic Horn which had once belonged to Queen Susan and was supposed to bring help to those who blow it. The help comes in the form of the children who had once been Kings and Queens of Narnia.
The children are sitting in a railway station when they feel themselves being tugged back into Narnia. They are somehow transported to Cair Paravel, their former castle, which is now a ruin. There they are found by a dwarf who brings them back to Caspian. Together with Caspian and of course, Aslan, who also comes to help, they defeat the Telmarines and set Caspian on the throne of a united Narnia. At the end of the story, Susan and Peter are told that this will be their last trip to Narnia as they are growing up.