Peter Debruge Chief Film Critic Like “Testament” — the 1983 made-for-TV movie that imagined the fallout, both nuclear and psychological, after an atomic bomb is dropped on American soil — “Leave the World Behind” depicts a plausible doomsday scenario from the perspective of a handful of ordinary characters. Not military experts, not scientists, but two families obliged to shelter under the same roof out in the East Hamptons while something scary unfolds a few hours away, off-screen, in New York.