In "The Fox and the Forest," what is the warning?

Throughout the first several pages of "The Fox and the Forest," William and Susan receive several warnings and signs that they are about to be captured.
The first line of the story foreshadows that something is wrong. The narrator begins by saying "there were fireworks the very first night, things that you should be afraid of perhaps, for they might remind you of other more horrible things" (Bradbury, 17). Although fireworks are typically beautiful, right from the start the reader should sense that something is wrong.
As William and Susan are enjoying themselves, Susan is unsettled by a man who is watching them, and she notices that the man is surrounded by several bottles of liquor (a warning sign that this man is from the future, since only time travelers would have such excessive amounts of alcohol, due to its unavailability in the future). This man examines the way that Susan and William dress and act, and he confronts them after noticing that William does not hitch up his trouser legs before he sits, a sure indication that he is not used to wearing these clothes.
William and Susan think that they have escaped the man who is pursuing them, but they get a call that night during which the man tells them, "The rabbits may hide in the forest . . . but a fox can always find them" (Bradbury, 23).
William kills the man with his car, and he and Susan again think they are safe in the company of an American film crew. However, one man in the crew says that he believes Susan would be a great actress and would star in a "story of suspense . . . a man and wife, like yourselves" (Bradbury, 29). As the man continues to describe this hypothetical story, it is clear that he is also hunting them and that this "movie" is their life story.