Chekhov’s gun is the literary technique whereby

Chekhov’s gun is the literary technique whereby an element is introduced early in the story, but whose significance does not become clear until later on. For example, a character may find a mysterious object that eventually becomes crucial to the plot, but at the time of finding the object, does not seem to be important.

That’s Anton, not Pavel (who in turn should not confused with tennis player Pavel Chekhov (who has a brother named Anton!)).

• antonchekhov