The Pevensie children go to Narnia for a second time in the novel, Prince Caspian. This story takes place only a year (in our time) after the children had gone to Narnia the first time, but when they arrive in Narnia, hundreds of years had passed in Narnian time. During that span, Narnia was conquered by the Telmarines and the old Narnian creatures had died or had been in hiding for years. This adventure story begins with one of the Telamrine rulers, Caspian, who had been displaced from his throne as a child by his evil Uncle Miraz. As Caspian flees for his life, he finds the Old Narnians in their hiding place. The Old Narnians rally around him when he promises to create a Narnia for both men and beasts, forming an army to attack Miraz and return the land to its rightful ruler. Initially, the attack fails, but when 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 by the call of the horn. They are transported to Cair Paravel, their former castle, which is now lying in ruins. There they are found and delivered to Caspian. Together with Caspian and 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.
Quotes from Prince Caspian by C.S. Lewis