“A Sound of Thunder” skillfully uses foreshadowing to build tension and create mirroring events that unfold in the narrative. This technique serves the subject of time travel well and reflects some of the central themes of the story. As the characters move between the past and the future, certain events mirror each other, creating foreshadows that sustain a sense of suspense.

The story begins with Eckels reading a sign on the office wall that touts the company’s slogan. Upon his return from the past, he notices the same sign, but the language has changed. The foreshadowing of this sign illustrates that even the minutest alteration in the past can result in profound consequences.  

The same mirroring of events takes place when he discusses the election results with the man behind the desk. Both are relieved that Keith has been elected, given that Deutscher threatens to create “the worst kind of dictatorship.” This conversation foreshadows the change in history, establishing the seriousness of what might happen after the safari, and it mirrors the future when dictatorship will prevail.

Other instances of foreshadowing appear throughout the story. Travis’s explanation of why they need to stay on the path hints at the political ramifications of stepping off it: “Queen Elizabeth might never be born, Washington might not cross the Delaware, there might never be a United States at all.” Even Lesperance’s explanation of the “paradox” of not being able to meet oneself in the past foreshadows the fact that Eckels will never be able to set matters right in the end. Ultimately, the story’s title foreshadows events in mirror. The footsteps of the dinosaur thunder, it thunders as it falls, and the final crack of Travis’s rifle thunders as well.