When Christopher gets home from school, his father is still at work. Christopher leaves his book on the kitchen table while he watches a movie about underwater creatures. He likes that science is always making new discoveries, and likes to imagine himself in a submarine.
Christopher isn’t particularly protective of the book, which suggests that he doesn’t fully understand the importance of Mrs. Alexander’s revelation. His appreciation of scientific discoveries makes sense, because he likes knowing how the world works.
When Ed gets home, he says hello and goes into the kitchen. A little while later, he comes back to Christopher holding Christopher’s book, which he has read. He asks whether Christopher really talked to Mrs. Alexander, and Christopher admits he did. Ed is very angry, and Christopher tries to tell him that he didn’t do anything Ed told him not to, but Ed shouts at him for snooping in other people’s business. When Christopher continues to make excuses, Ed grabs him by the arm, which he’s never done before.
As much as Christopher has tried to stick to the truth and keep his promise just enough to satisfy his own conscience, Ed makes him face the fact that in practicality, he has broken his promise. Christopher’s book, which has seemed like a fun school project so far, now takes on much heavier implications, since it has given away all of Christopher’s secrets. He has been consciously writing for an audience, but the one person he didn’t anticipate as an audience is his father.
Christopher hits his father again and again, and his memories black out temporarily. When he becomes aware of himself again, both he and Ed are hurt. Ed goes outside and throws Christopher’s book into the trashcan, and then gets a beer.
Christopher’s lapse in consciousness makes it difficult to lay blame in this fight. However, it’s clear that Ed is not dealing in a productive way with the fact that Christopher knows about his mother’s affair.