What is foreshadowing and how does foreshadowing begin to play into the story, especially with regard to Langdon?

Foreshadowing is a literary method of hinting at things to come later in a story. Foreshadowing plays a role so far because Langdon keeps seeing similarities in this scenario to the one he encountered in Vatican City where he almost got killed. This foreshadowing increases the suspense of the story because the reader fears for the safety of Robert Langdon.