Hilde cannot figure out what happened to Sophie and Alberto and she thinks she must read the book a few more times to find some clues. Sophie and Alberto escape from Albert Knag and find themselves in Oslo. Alberto assures Sophie that they are outside of Hilde's father's reach, but points out that he may have wanted them to escape because he created the chaos that let them slip away. Sophie figures out that people cannot hear them, and Alberto points out that even though they are no longer a part of the major's book they are also not like other people. They take a make-believe car and drive off to be there when Albert Knag meets his daughter in Lillesand.
Albert Knag lands in the Copenhagen airport and is immediately paged. He is given a letter, from his daughter, which gives him some instructions. Then as he passes a deli he sees another envelope with his name on it that tells him what to buy in the store. Albert Knag thinks he is being observed and he spends the rest of his wait in the airport following instructions from letters and is quite paranoid on his plane ride home.
Sophie and Alberto are driving, but Sophie is concerned because they can go right through everything and she thinks they are less real than everything around them. Alberto says the opposite is true—they can go through everything else because they are more solid than the rest. They are spirit, and spirit can move through anything. They stop for coffee and meet an old woman who is also of spirit, out of Grimm's Fairy Tales. She tells them they are part of the invisible people and they see many others whom they had once thought were imaginary.
Albert Knag realizes his daughter has given him a dose of his own medicine and it continue the entire trip home. Hilde has messages to him everywhere. Finally he arrives at home. Just at that moment Sophie and Alberto arrive and Sophie runs down to Hilde. She tries to speak to her, knowing she cannot succeed, but is surprised to see that Hilde seems to sense something. Then her father calls her name. Hilde and her father talk about everything, laughing and enjoying themselves, and Hilde again thinks she hears something. What she heard was Alberto honking the car horn. Sophie is sad that she cannot live a real life but Alberto points out that they will live forever and that there is much for them to do.
While Hilde's father tells her about the universe and the Big Bang, Sophie tells Alberto she thinks they can have an effect in Hilde's world. She hits Hilde in the face with a wrench and Hilde yelps in pain, thinking a gadfly stung her. Hilde thinks she feels Sophie's presence. Alberto is impressed. Albert tells his daughter that we are all a part of the same whole, since everything started with the Big Bang. So an attempt to understand the universe is an attempt to understand ourselves. Sophie and Alberto manage to get the rowboat loose, and Albert makes fun of his daughter by suggesting that maybe Sophie did it.
The question of free will is one that philosophers have been addressing for ages. It is also one of the main issues throughout Sophie's World. The question that can always be asked of our actions—are they determined—is exactly what we must ask of Sophie and Alberto. Their case makes the argument very explicit. We know that Albert Knag has written the book in which they are characters. They know that as well, but they do not know how the book will end. Sophie and Alberto feel as though they are in control of their actions even though they know that Albert Knag has made them feel that way. The same problem applies to our lives. While it is not as obvious as it appears for the characters in the book, all of our actions could also be predetermined. The fact that, unlike Sophie, we do not know that they are determined, does not change the situation. Many of the philosophers that Sophie and Alberto have studied dealt with this issue. Some of them felt that everything is determined, that we are all subject to the laws of nature and our every action and thought follow from them. Others believe that with consciousness comes our freedom. The problem is that if things are determined and we do not have free will then even our debates about the subject are fated to happen. What we feel about what is happening does not matter, because we cannot change what will occur. Such a thought is depressing, but it does not seem that Gaarder thinks along those lines.