How did Jem save Atticus from the mob in To Kill a Mockingbird by Harper Lee?

In Chapter 15, Atticus tells his children that he is going downtown and carries a long extension cord with a light bulb at the end when he leaves home. Jem notices Atticus takes his car and decides to follow his father instead of going to bed. Scout and Dill tag along as Jem leads them to Tyndal's Hardware, which is close enough to the jailhouse that they can see Atticus sitting out front of Maycomb's...

In Chapter 15, Atticus tells his children that he is going downtown and carries a long extension cord with a light bulb at the end when he leaves home. Jem notices Atticus takes his car and decides to follow his father instead of going to bed. Scout and Dill tag along as Jem leads them to Tyndal's Hardware, which is close enough to the jailhouse that they can see Atticus sitting out front of Maycomb's jailhouse. They watch as the Old Sarum bunch arrives and encircles Atticus. As they watch, Scout becomes curious and decides to run into the middle of the group of men. Shortly after she enters the circle, Jem and Dill follow her out. Atticus sees his son and says, "Go home, Jem. . . Take Scout and Dill home," but Jem refuses to obey his father's commands (Lee 94). Jem knows his father is in a dangerous situation and refuses to leave his side. Despite Atticus's pleas, Jem does not go home. Fortunately, Scout recognizes Walter Cunningham's father and eventually gets his attention after she attempts to start a conversation. Walter notices Scout and realizes the error in his judgment. Walter then tells the gang to disperse, and noone is harmed. Jem's presence and refusal to leave the scene protect and save Atticus from the Old Sarum bunch.