The Midnight Visitor is a story about two rival spies, Ausable and Max, and a writer named Fowler, who becomes intrigued by the spy world. The tension escalates when Max threatens Ausable for sensitive documents, but clever deception leads to Max's demise as he jumps out of a non-existent balcony. The story highlights that appearances can be misleading, as Ausable’s clumsiness belies his cunning nature.