Jonathan reveals that Selenna and Isaac Izard were the previous owners and they were involved in evil magic. They cannot find the source and Jonathan tends to hide the sound by having dozens of clocks spread around the house. Meanwhile, there is a ticking in the walls at Jonathan's house that no one can identify. When Tarby begins to show more signs of losing interest in Lewis, Lewis wildly makes the claim that he will raise someone from the dead. Later, Lewis discovers that Tarby told his father about the evening, though Lewis had asked him not to do so. He invites Tarby over for an evening, and Jonathan causes the moon to eclipse during the visit. When a very popular boy named Tarby seems to befriend Lewis, he becomes determined to do anything in order to keep Tarby's interest. He is overweight and performs poorly at sports. He is beginning a new school, but he is having the same problems that have always followed him. Lewis quickly forgets this mystery as he struggles with the details of his own life.

They cannot find the source and do not know the meaning, but Jonathan believes it has something to do with the previous owners of the house, Isaac and Selenna Izard, who both had magical powers.

It sometimes ticks faster and sometimes more loudly, but it never stops. From anywhere in Jonathan's house, they can hear a ticking clock. Lewis is in the house only a short time when he learns that Jonathan and Florence are both magical and that they have a mystery on their hands. Lewis quickly feels at home with his uncle, and the next-door-neighbor named Florence becomes the best friend of Lewis. Lewis Barnavelt is a 10-year-old boy who moves in with his Uncle Jonathan after Lewis's parents die in an accident. (Note that an earlier version of this book was published by Dial Press in 1973.) The following version of the book was used to create this study guide: Bellairs, John.

House with the clock in the walls book