In To Kill a Mockingbird, where does Atticus go on Sunday night in chapter 15? Why does Jem want to follow him?
There are many red flags in chapter 15 that signal to Jem that something important is going on with his father, Atticus. First of all, on Saturday night, a group of men from town, including Link Deas and Sheriff Tate, show up on the front lawn to discuss the fact that Tom Robinson will be in the Maycomb jail Sunday night--the night before his trial. The children overhear that the men of the community are concerned that the Cunninghams might do something crazy with Tom in town. Atticus doesn't think anything will happen, but the crowd has a pretty intense discussion about it from what Scout and Jem can hear.
Then, on Sunday after dinner, Atticus gets a long extension cord with a light bulb on the end of it, bids the children good night, and takes the car. The children know that Atticus is acting peculiarly because he never takes the car anywhere in Maycomb. Based on what he has seen in the last day or so, Jem is a little concerned for his father and feels the need to find out what is going on. As a result, Jem and Scout sneak out, pick up Dill, and go looking for Atticus. They find Atticus sitting outside of the jail next to Tom's cell reading. The cord with the light was running through the bars of the second floor window and hung down to help him see what he was reading.
In chapter 15, Atticus leaves the house after supper. He takes an extension cord and a light with him. Because he takes his car, Jem becomes worried about him. Jem decides to follow Atticus because he knows that since the group of men came to the house the night before, he feels Atticus may be in danger. Jem feels that as long as he is able to see Atticus, he won't worry as much about him. He finds Atticus sitting guard in front of the jailhouse. Because Tom Robinson has been brought back to Maycomb, Atticus knows that a lynch mob may be coming, and he wants to stop them from taking the law into their own hands.