In To Kill a Mockingbird, how does Jem's broken arm connect with Boo's story and Tom's story? How does the mockingbird connect them all?

The novel develops two plots, separately and then simultaneously: the children's attempts to discover the truth about Boo Radley and the prosecution of Tom Robinson, who is innocent, when he is charged with raping Mayella Ewell. These two story lines converge in the novel's conclusion when Mayella's father, Bob Ewell, attacks Jem and Scout, the children of the man who defended Tom Robinson in court. It is during Ewell's violent attack that Jem's arm is broken. Ewell would have killed them both, but Jem and Scout are saved by Boo Radley. As a result of this attack on the children, Boo Radley kills Bob Ewell, and Jem and Scout realize the truth about the mysterious Boo: He is a brave man who loves them and is willing to sacrifice himself to save them.

The mockingbird theme is central in the novel. Early in the story, Atticus explains to Jem why he is not to shoot mockingbirds with his air rifle. According to Atticus, mockingbirds are innocent and harmless; they do not threaten or destroy anything or anyone. They bring only goodness into the world. Thus Jem, Scout, Tom, and Boo all can be viewed as mockingbirds.