This is an introduction to the idea of infinity and transfinite numbers in mathematics, but aimed at non-mathematicians. As such, it is sometimes seen on UK television in what used to be the Open University slot (BBC2 after midnight). It is told through puzzling conversations between guests and the captivating receptionist, and in discussions between guests themselves.
It is not intended as a film with a plot, so don't expect one (by that yardstick I'd rate it at 3, saved from a lower score by its brevity). However, if you want an inspirational insight into the joys of infinity (and infinity plus one, infinity plus two, ...), then start here, and record it to re-watch later. On that basis, I vote an 8.
Warning: this film could make your brain hurt.