It is difficult to know what to think about this film, or how to feel — except that it consists of 103 thoroughly absorbing minutes, largely of two people talking to each other. It begins with an internet chat room, where a 14-year-old girl arranges to meet a man in person. We then join them as they meet: he is Jeff, a photographer in his early thirties who lives alone; she is Hayley, a precociously intelligent teen who would not look out of place playing Peter Pan on stage. Hayley soon finds an excuse to suggest that they go back to Jeff’s apartment — where she spikes his drink…

…And when Jeff wakes up, Hayley has tied him to a chair. Her intention is to take revenge, for she believes him to be a predator — which he is, for she soon finds the photographic evidence, including a picture of a local girl who has gone missing. Did Jeff kill her? He says not, but Hayley doesn’t believe him.

Later, when Jeff tries to escape, she stops him by wrapping his head in clingfilm; when he next wakes, Jeff is tied to a table — to find Hayley dressed in surgical scrubs, with her father’s medical textbook, and about to perform an operation that Jeff would prefer not to contemplate. So the movie continues, a game of cat and mouse, with Jeff occasionally gaining the upper hand, though not for very long — until Hayley demands he make the ultimate choice.

This is the kind of film that stands or falls by its central performances, and both are excellent. Hayley is portrayed brilliantly by Ellen Page (who played another precoious teen a couple of years after this in Juno, but the two characters are nothing alike). It should be absurd, the idea that a small, skinny, waif like Hayley should be able to overpower a grown man who’s a foot taller than her — it is absurd, and both characters know it (what’s the point in Jeff calling the cops, who’d believe him). And it’s not that Hayley is invincible: yes, she came prepared, she has her weapons and her defences — but at the moments they fail, we see the scared girl inside, who knows that Jeff could overpower her easily if he had the chance.

But perhaps Hayley’s greatest defence is one that can’t be taken away — her inscruatble nature. There’s nothing of the femme fatale about Hayley, nor does she have brute strength; she’s menacing because we (and Jeff) don’t really know who she is or where she came from — but we do know that she’s implacable. With Page’s performance, there is never any doubt that this situation is reality, however absurd it may be in theory.

Jeff is played by Patrick Wilson and, whilst his performance may not have quite the same impact as Page’s, that’s really only a matter of degree. We don’t learn much at all about the two protagonists, so it’s hard to judge what to feel towards Jeff, especially at first — ostensibly he’s the victim of the piece, but Hayley says he’s a monster, but then again,  we only have her word for that for a good while. Only gradually does Wilson reveal glimpses of Jeff’s true nature underneath. Layered, subtle performances from both leads.

As all this may suggest, the morality of the film is complicated. You can’t root for Jeff, because of what he’s done and may do again. But can you really root for Hayley, after what she does? The movie, it seems to me, does not come to any firm conclusions, leaving everyone to make up their own minds individually.

What’s not in doubt is that Hard Candy is a very striking piece of film-making. Despite its theme, there is hardly anything gratuitous or graphic in it (there’s some blood on a scalpel, and that’s about it); so much of the film’s effect is achieved by suggestion and implication. The visual style is also distinctive, with claustrophobic close-up shots and an often washed-out palette.

In short, Hard Candy is not a comfortable film to watch — but it keeps you watching nevertheless.