This all-new special is an "Encyclopedia Galactica" of non-Earth life forms, and an investigation into the latest scientific understanding of life beyond planet Earth. ALIENS: THE DEFINITIVE GUIDE showcases the extraordinary scientists who are currently grappling with extraordinary questions about alien life including: what will aliens really look like?; how will they sound?; what might their words look like; and, of course, will they come in peace? This two-part special takes viewers to stunning, remote locations on Earth as well as elsewhere in the universe.