Jem and Scout are mostly just curious about their father's defense of Tom Robinson in Part One of To Kill a Mockingbird. But as the trial approaches, they begin to worry for their father's safety. When a group of men meet in Atticus's front yard just days before the trial is supposed to begin, Jem assumes it is a "gang" out to harm him.
"They were after you, weren't they?" Jem went to him. "They wanted to get you, didn't they?"
They were only Atticus's friends and supporters, but Jem later tells Scout that he's scared.
"Scared about Atticus. Somebody might hurt him."
The children knew something was amiss when Atticus suddenly left the house late one Sunday evening. When the children followed him, they found him confronted by a group of men in front of the jail. It was the next day when Scout realized that Atticus's life had been in danger from the lynch mob that had planned to take Tom from the jail.
The full meaning of the night's events hit me and I began crying.
Jem told Atticus that Mr. Cunningham would "have killed you last night when he first went there." But Atticus tried to calm his kids, assuring them that although it was a mob, it was "made up of people you know...," and that his life was never really in danger. After the trial, however, they will discover that there is another man who has a reason to harm Atticus--and his children.