Smile is not the most original entry in the new wave of gentrified horror. Its biggest debt is owed to It Follows, the 2014 film about a death curse that’s passed through sexual intercourse. Smile takes this premise and raises the stakes, imagining a curse transmitted not by sex but by performative suicide. If you witness it, you’re next. This conceit may not be original, but Smile loads its two hour runtime with a strong lead character, an oppressively dark tone, and a resonant commentary on mental health.

Our focaliser is Rose Cotter (Sosie Bacon), a psychiatric doctor with high minded, Hippocratic beliefs. Unlike her sister – a smug and vicious kept woman – Rose eschews materialism for a humble duty to her patients. Course, she’s not short of a few bob herself, but that’s utterly incidental in the horrific psychodrama that will unravel for Rose over five terrifying days.

It begins with a meeting between Rose and Laura, a PhD student who witnessed her professor’s brutal suicide. Highly disturbed, Laura falls to the ground in a blind panic as she appears to lapse into a psychotic episode. However, just as Rose calls for help, Laura rises and stands eerily still, staring at Rose with a fixed, toothy grin. She then takes the shard of a broken jug to her throat, cutting it open with bloody, fatal results.

Horrified, Rose is given a week off to “clear her head”, yet no amount of R&R is going to get her out of this hole. First, she sees apparitions of Laura in the dark corners of her home. These moments are staged well, showing us just the outline – and smile – of Laura against the inky darkness. A series of jump scares follow as Laura tightens her grip on Rose’s psyche. My friend and I were caught at least one time each. You probably will be, too. Indeed, Smile is likely to attract a popular audience seeking jumps and screams. However, I suspect most audiences will leave not with an energised terror but with a hopeless sense of dread and depression.

This is because Smile grounds its supernatural horror in the terrible reality of psychosis. Rose’s visions get stronger from hour to hour, unravelling her mental state in front of friends and family in numerous painful moments, especially a child’s birthday party that takes a harrowing and humiliating turn. The reactions of those closest to Rose range from cowardly to plain selfish. Her sister is far too arrogantly comfortable to empathise with mental illness. Such things aren’t supposed to exist in her manicured little world. Arguably worse is Rose’s fiance Trevor (Jessie T. Usher), who is completely disconnected from and even contemptuous of his partner’s struggle. Rose’s boss Dr. Desai (Kal Penn) takes a medical view of the situation and supports as best he can, but Rose’s one true ally is her ex-lover Joel (Kyle Gallner), a police detective.

With his authority and access to police information, Joel is perhaps the only rock on which Rose can finally rest. No one else will listen to her and no one else can help her like Joel can, either. They begin to make some progress in rationalising Laura’s death, connecting the dots of a bizarre phenomenon, but any semblance of control is soon destroyed by the curse, hurtling the film towards a haunting and bloody conclusion.

Smile earns its ’18’ rating with sequences of intense supernatural gore. People are stabbed, faces are torn off. There’s even a monstrous figure not unlike a creature from The Thing or the Silent Hill video game series. But again, despite its grisly supernatural flair, the real horror of Smile is in its sense of reality. Parker Finn’s film is a metaphor for a severe kind of mental illness that places its subject, Rose, into a fearsome, lonely existence. Ultimately, Smile is tragic rather than terrifying.