Nelson DeMille spins an ephemeral mystery out of the real-life crash of TWA Flight 800 in July 1996 in Night Fall. A pair of adulterous lovers film themselves having sex in the Long Island surf — and discover that the tape captures more than their private fireworks. The couple vanishes, along with the film, leaving a lens cap and a hotel blanket on the beach to tantalize investigators. Did they keep the tape? Does it prove that a missile (not mechanical failure) brought down the plane? Five years later, John Corey, the wisecracking detective from DeMille’s Plum Island, hunts for the couple using enough old-fashioned sleuthing skills to keep this preposterous, overlong novel moving.