Every good tale of adventure and suspense needs a good MacGuffin, a plot device that focuses the intentions of the central characters and gives the story coherence. Often that Macguffin is the title character - "The Purloined Letter" or "The Cask of Amontillado." Jo Rowling's Harry Potter books are masterful examples: the philospher's stone, the chamber of secrets and so on.
This seemingly obvious fact was unknown to me until I translated a short article on Alfred Hitchcock from the Spanish. It helps explain why the fiction I try to write has a way of running out of steam.