The Father is not out in the UK until next month, but we already know plenty about it. We know that its script won an Oscar for the uncanny way it dropped the viewer into the mind of someone with dementia. We know that Anthony Hopkins gave such a harrowing, desperate performance that he also won an Oscar. Perhaps you even read the New Yorker interview with Hopkins about the role, which inspired him to recount the circumstances of his own father’s death in devastating detail. Basically, we know that The Father is quite a dark film.

Someone should really mention this to whoever is in charge of making the posters. Because it’s difficult to remember a film that has been this relentlessly miscommunicated. In the latest one, Hopkins sits with a knowing half-smile on his lips while Olivia Colman beams at him. Aside from a lot of boasting about all the awards it won, that’s all there is to go on. “Look,” it coos, “here’s a film about a lovely old man’s lovely relationship with his lovely daughter.” Which, admittedly, might have more popular appeal than: “This is a horror movie about the agony of neurodegenerative dementia that awaits many of us.” But that isn’t really an excuse.

The previous posters have not been much better. The first did at least have a background, but it still featured Colman gazing adorably at a lovely old man. And the quotes didn’t help much, either. There were plenty about the acting – “Anthony Hopkins is stunning”, “Olivia Colman gives an affecting and tender performance”, that sort of thing – but not much about the film itself.

This is strange, because it isn’t as if The Father is wanting for effusive reviews. The Sydney Morning Herald called it “far scarier than anything Freddy Krueger ever threw at us”. The Boston Herald called it a “frightening dementia drama”. The New York Times called it “profoundly upsetting”. The Guardian’s Benjamin Lee said that “it’ll haunt me for weeks”. Stick any of those on a poster and audiences will have a much better idea of what they’re getting into.

Even weirder is that the trailer gets it. It is queasy and discombobulating, and features plenty of shots where Colman gulps back tears at the shadow of the man her father has become. Watch that and you’ll understand the reviews. But if your exposure is limited to the lovely poster, it starts to feel like a trick designed to get the King’s Speech crowd back into cinemas.

It might not be the most misleading poster of all time – that title still goes to the American poster for The Italian Job, where an anonymous gangster totes a machine gun next to a naked woman – but it comes awfully close.

The Father is a critical darling. It has the biggest awards in the business. It doesn’t need to fool viewers into thinking it’s a feelgood drama. That is, unless this was all a deliberate ploy to throw us off and make us doubt our own instincts, just like The Father’s lead character. In which case it’s an absolute masterwork.