Foreshadowing is a hint of what is to come later in any of several types of literature.

In Something Wicked This Way Comes, Ray Bradbury harnesses foreshadowing several times.

“The seller of lightning-rods arrived just ahead of the storm.” – Bradbury, Something Wicked This Way Comes. Chapter 1, First Sentence.

In the first sentence of chapter 1 of Something Wicked This Way Comes, Ray Bradbury warn us that a storm is coming, and I assure you that a severe storm does come later in this book.  Something Wicked This Way Comes is about the storm that hits the little town of Green Town, Illinois. On one hand, the seller of lightning-rods is warning two boys about the storm which will emit lightning that will strike one of their houses. But on the other hand, Ray Bradbury is alerting the reader that a terrific storm is about to shake them up, via the writing of his book.