There’s an argument that the less you know going into any film the better. Naturally there are some films this applies to more than others, and Exam is one such film. Eight young professional types go into a job exam/interview; the next hour-and-a-half is all mysteries and riddles — which is why you wouldn’t want to know too much.

The film occurs in real-time (more or less) in a single room. These are two narrative tricks I always enjoy the potential of. I’m not saying every film should be set in a single room and/or take place in real-time, but when pulled off well either is an enjoyable feat. Exam succeeds in both. Real-time is, I think, easy enough with the right story if you put your mind to it (though the Johnny Depp-starring Nick of Time fails to make it work, in my opinion), but making an engrossing and — even harder — exciting film set in one room is a challenging prospect. Even in a film like Cube, though it takes place on one identical set, the characters are actually moving from room to room.

Writer-director Hazeldine’s screenplay is inventive enough to keep the story rolling throughout the entire film, barely pushing the tale past the natural end of its ideas, while the direction and camerawork keep it visually interesting without tipping over into pointless flashiness. I suspect he may be one to watch, though almost 18 months after Exam’s UK release he doesn’t seem to have any directing projects lined up (at least according to IMDb).

Such a contained story relies heavily on its characters and the actors’ performances. Largely a cast of un- (or little-) knowns, all are decent — one or two may be subpar, but I’ve seen a lot worse. I don’t quite understand how some viewers can find White, played by Luke Mably, to be a completely likeable character in spite of his obvious flaws — he has his moments, but surely he’s not agreeable overall? Not a jot. That said, his is the standout part, a scene-stealing performance from Mably. There’s no clear-cut audience-favourite, which (from reading a few reviews) seems to be a problem for some viewers. As far as I’m concerned, it’s a good thing: never mind the realism of there being one perfect person every viewer will love, audience-favourites will either predictably win or be shockingly dispatched, so what’s the point?

As it is, various viewers may root for various applicants; and even if you like none of them, it’s not necessarily a problem: the audience is more-or-less positioned as Candidate 9, solving the puzzle along with the characters on screen. It’s the mark of a good mystery that it drags the audience in to trying to guess it too. (Or perhaps it would just be the mark of a bad mystery that it couldn’t even manage that, so maybe it’s not a point of praise as much a point of not-criticising. You may take your choice on this point.) There are plenty of red herrings tossed liberally around, many of which are well-used but perhaps don’t have the part you’d expect them to play come the ultimate revelations. Which is fine — it’s quite nice to find a plot that doesn’t feel the need to tie everything in to its reveal; a plot that can wrong-foot you by occasionally focusing on something that’s ultimately irrelevant.

The most major flaw is perhaps the final few minutes. Exam ends with a compact array of twists, all of them well-structured — they grow neatly from what we’ve been told already, as any good twist should, rather than hurling themselves in from nowhere for the sake of it — but there’s also rather too much information. I like finding out what was going on, but ambiguity can be good too (look at Cube) — so on one hand I’m pleased we’re told things, but on the other I think it’s overdone, providing too much backstory in a rush to explain everything the filmmakers have dreamt up. Dialled back a bit it would hit the nail on the head.

I also don’t know how it well the film would stand up to repeat viewings. The advantage it has in being a small, little-seen film is that you can go in knowing virtually nothing about what’s going to happen, and play along with the guessing game the characters are involved in — this is the film’s primary joy. But with all the answers revealed, would it have as much to offer when watched again? I can’t answer that, obviously. It’s certainly possible — Cube (which I’m mentioning repeatedly because there are numerous similarities) still works — but there’s no guarantee. The story poses some thematic questions — about motivation, morals, that kind of thing — for those who care to ponder them, and films that invite pondering tend to invite repeat viewing; but then again it works equally well (better, ultimately) as a straight-up “what’s going on?” thriller.

Nonetheless, as a first-time experience, Exam is an intriguing and entertaining head-scratcher. It was a very early contender for my end-of-year top ten — and four months later, still is. A borderline 5.

The UK network TV premiere of Exam is on Movie Mix (aka more>movies) tonight, Wednesday 18th March 2015, at 9pm.