What is the significance of the incident at Judge Taylor's house?

Not long after the end of Tom Robinson's trial, with the
predictable guilty verdict, it becomes apparent that the perpetual drunk Bob Ewell has
not forgotten that Atticus made him look like a fool on the witness stand (admiittedly,
not a difficult task).  He is overheard by some townspeople making a not-so-veiled
threat toward Atticus, and when he encounters Atticus, Ewell actually spits on him.  One
evening when Judge Taylor is reading in his study late at night, sounds are heard that
suggest that someone is prowling around his home, and the reader easily infers that it
is probably Bob Ewell, still up to no good.  These events lead up to the climax of the
novel on Halloween night when Ewell tries to kill Scout and
Jem.