I envy anybody who goes to see Predestination with absolutely zero idea of what it's about. If this is you, then stop reading this immediately, block out all other synopses and reviews, and watch the film.

I post this warning not because Predestination is great. It's merely okay. But when a movie's enjoyment depends greatly on its plot twists, the problem is that you're always on the lookout for them. Twists only work when they surprise. Expecting them often leads to disappointment. And it's hard not to hear or read two sentences about Predestination without learning that you're supposed to expect some nifty plot twists.

After a short, purposefully vague opening montage featuring Ethan Hawke, we find ourselves in 1975 New York City. Hawke is working as a bartender when a man walks into his bar and promises to tell him the greatest story he's ever heard. It's instantly clear that this "man" is played by a woman – Australian actress Sarah Snook, good but not great in a challenging role – but the film doesn't dance around this for long; within minutes, he begins his story with, "When I was a little girl..."

First twist – an overtly obvious one – down. Several more to go. I won't spoil them here, even if the film's very marketing emphasizes a particular science fiction element that's only revealed about halfway through the run time (when the plot finally kicks in; until then, the film is mostly just the stranger telling Ethan Hawke his/her back story).

It's hard to tell whether the Spierig brothers, whose script is a faithful adaptation of Robert A. Heinlein's 1958 short story All You Zombies, are mediocre filmmakers, or if they don't really care whether you can suss out the twists. The foreshadowing is often so blatant and clunky that my wife – who correctly guessed every plot twist ahead of time – wondered if it was all on purpose.

Those twists ultimately build up to a mind-boggling and weirdly touching revelation – all courtesy of Heinlein. For this thought-provoking conclusion alone, Predestination is worthwhile. But it doesn't appear to add anything to Heinlein's story, and in fact this strange tale may contain more genuine surprise on paper. Aside from that, although it has its moments, this is by no means an exceptional film.