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?
With a narrative told in retrospect, To Kill a Mockingbird begins with Scout's recounting of Jem's having broken his arm when he was almost thirteen. This mention of the incapacitated arm foreshadows something that has happened to Jem as well as the once-injured and withered arm of Tom Robinson. The trope of the mockingbird ties to these characters.
In Chapter 1 Scout narrates that she believes that her brother's injury has as its cause Bob Ewell, but Jem insists that the story began with Dill's arrival and his interest in the mystery about Boo Radley. Because of Dill's insatiable curiosity about the "haint" named Arthur Radley, the children play near the Radley house frequently so that Boo is able to watch them and vicariously participate in their fun. In fact, it is because of his vicarious and interactive experiences, such as mending Jem's pants, leaving gifts in the knothole of the tree, and placing a blanket on Scout's shoulders on the cold night of the fire that Boo becomes the friend of Jem and Scout. Because of this emotional connection to the children, Arthur Radley, a "mockingbird," risks personal injury in order to rush to the defense of Jem when he is attacked by Bob Ewell.
Of course, the reason Scout and Jem are assaulted by Bob Ewell is the fact that Atticus has defended the "mockingbird" Tom Robinson against the false charges of the Ewells. While Ewell is on the witness stand, Atticus exposes the ignorance and falseness of Bob's and Mayella's testimonies. After the trial, the vindictive Bob Ewell spits in Atticus's face, sneaks into Judge Taylor's home, follows Helen Robinson, and, finally, attacks the "mockingbirds," the innocent Finch children.
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.