In spite of some feeble romantic comedy (notably in the android factory sequence) and an occasionally trite musical score, this is an accomplished and enjoyable sci-fi film which contains more ideas than many movies made on far higher budgets. It's about a team of scientists who construct a mirror to the future. The mirror becomes a door, and they get stranded on the wrong side. The middle part has some relatively standard sub-Wellsian plot material involving two future civilisations; but the ending, in which they get caught in a time-trap, is utterly amazing and completely original; it even compares favourably to the trip sequence in 2001: A Space Odyssey. The cameraman, incidentally, was Vilmos Zsigmond.