At the beginning of Chapter 27, Scout mentions three events that indirectly involved her family and Bob Ewell. First, Scout recalls how Bob Ewell was fired from the WPA for laziness and blamed Atticus for "getting" his job. The second strange thing happened to Judge Taylor. On a Sunday night, Judge Taylor was quietly reading alone in his home when he heard an irritating scratching noise coming from the rear of his house. When he got up and went to the back porch, he found the screen door swinging open. Judge Taylor then saw the shadow of a man running from the side of his house. When Judge Taylor's wife returned home from church later that night, she found her husband reading with a shotgun over his lap. Bob Ewell was the man responsible for prowling around Judge Taylor's home in hopes of seeking revenge. Fortunately for Judge Taylor, Bob Ewell is a coward and did not go any further while he was snooping around his home. 

Judge Taylor was home alone on a Sunday night and heard a noise outside.

Bob Ewell begins to make his mark after being dissatisfied with the trial.  For one thing, he spits in Atticus’s face and threatens him.  He also follows Mrs. Robinson and seems to prowl around Judge Taylor’s house at night.

One Sunday night, lost in fruity metaphors and florid diction, Judge Taylor's attention was wrenched from the page by an irritating scratching noise. (Ch. 27)

All he sees is a shadow, but since Mrs. Robinson is also being followed and it was well known that he lost his job with the WPA almost as soon as he got it, everyone assumes it was Bob Ewell prowling around Judge Taylor’s house to get revenge.

These incidents demonstrate Bob Ewell’s downward spiral and the people he blames for it.  They also foreshadow his later altercation with Boo Radley when he tries to attach the Finch children.  Ewell is nothing but a coward, but he can’t accept what happened at the trial.  He blames Atticus and Judge Taylor for having a fair trial, even though Tom Robinson was actually convicted.  The fact that the jury even deliberated showed that they didn’t believe Bob Ewell, and that angered and haunted him.