In Chapter 28 of "To Kill a Mockingbird", how does the reader get the sense that Jem and Scout are in danger?

At the beginning of Chapter 28, Scout and Jem experience a "false" attack from Cecil Jacobs on the way to the pageant. Cecil's prank, along with the fact that it is Halloween night and they are walking past the Radley place, create an ominous mood that will extend through the entire chapter.

Lee juxtaposes the "fun" dangers such as Cecil's attack and the House of Horrors at the pageant with the real terror of Bob Ewell's attack. Prior to Bob's attack, Lee builds anticipation and tension with his quiet footsteps following the children home. As Scout and Jem try to figure out what is happening to them, the reader already knows they are in mortal danger.