The movie I am thinking about is Pontypool, based on Tony Burgess' novel, Pontypool Changes Everything, and directed by Bruce McDonald. It's from a few years back, but I know very few who have seen it. (There are lots of spoilers ahead.)
Pontypool is essentially a zombie movie. Some of the most used zombie tropes don't really apply in the movie (the "zombies" aren't actually dead and you don't have to be bitten to be turned, among others), but it follows the now-familiar story arch of a single victim infecting others until the central characters are left hiding from the zombie hoard.
What makes Pontypool different is the central conceit of the movie, which centers around the way the infection spreads.
From the outset, it's obvious that the movie will be centered around language. We hear Grant Mazzy, a talk radio host and protagonist of the story, telling a curious story about the name "Pontypool," the town that is the setting of the film. He quotes Norman Mailer about the power of certain coincidences before major events and we know that "something big is about to happen."
I think it is safe to say that if you are not drawn in by that opening monologue, this movie is probably not for you. It's not artsy or intentionally snobby in any way, but it's smart, really smart, in the way that very few horror films are.
Any horror story worth it's salt addresses important themes, and zombie films are some of the most conspicuous examples. In my opinion at least, zombie films tackle the question of what it means to be a human being, and when are we least in touch with our humanity. Two of the most notable examples of this are from George Romero, the grandfather of zombie flicks.
The original Night of the Living Dead was set in 1968 at the height of civil unrest in this country. The climax of the film comes when the hero, Ben, the sole African-American character, is gunned down by the police who have mistaken him for a zombie. The police officers are immediately transformed into the movie's villains, with almost as little to redeem them as monsters they were hunting.
Romero's sequel, Dawn of the Dead, dealt similarly with the mindless consumerism that was fast becoming the norm in the mid-70s. The film's zombies return to a shopping mall where they had spent senseless hours when they were living, only to continue their old habits.
Pontypool likewise engages us through metaphor about the way we use words in our culture. AM radio — that bastion of shock jocks, right-wing fear mongers, and conspiracy theorists — serves as the backdrop of a world gone mad with language. Words have lost their meaning, they are tossed about carelessly, and used thoughtlessly. Language, which is at the core of our humanity and separates us from much of the other life on the planet, has become the vehicle of dehumanization. The virus isn't passed through biting, it's passed through words.
Like I said, it's smart stuff.
The film's climactic scene occurs when the station manager, Sydney Briar (Lisa Houle), becomes convinced Mazzy is about to kill her and becomes fixated on the word "kill," indicating she is becoming infected. Mazzy saves her by telling her, "Kill means kiss," (yeah, do your own armchair psychology on that one) and they do kiss. Once they've discovered the tool to save others — talking nonsense on purpose, turning the meaning of words upside down — they go to the airwaves to help save the town. They are halted by a voice from outside (presumably police or national guard) demanding they stop broadcasting. There is a countdown and the screen goes black, leading us to believe the pair have been killed as the town is razed.
The epilogue features news broadcasts from around Canada (Pontypool is a real Canadian town) indicating the infection has spread.
The movie is a slow burn, with most of it taking place in the radio station studios, located in a church basement. So much of it takes place there, in fact, that I think it could be adapted quite successfully for the stage. There are only eight actors in the film, including those who are heard on the radio but never seen. The strongest performance is by Stephen McHattie (Watchmen, A History of Violence) as Mazzy, as boozy and washed-up of an anti-hero as you could want.
Pontypool does not shy away from the blood, but it is used only at critical points in the movie. The gore is truly disturbing, as McDonald uses it to show the victims' gradual deterioration into sub-human existence. The scares are more centered around mood, although there are a few jump-out moments. The true horror, however, is existential.
So much of the film is on-the-nose in terms of social critique, especially as regards the manner in which large groups of people become infected by words — words that have become stripped of their actual meaning and now just serve infect our minds. Dozens of these words and phrases come to my mind — "national security," "job creators," "family values" — words that are used to obfuscate rather than illuminate, words used to convey the very opposite of what their plain meaning might suggest. The mobs infected with these words are a cannibalistic horde, seeking to either infect others or destroy those who offer resistance.
Pontypool will not appeal to those groups, because it requires the viewer to engage with complex ideas. I don't mean to suggest that you are an idiot if you don't enjoy the movie; it will be too slow for many horror fans. But I think it's appeal lies in the way it stays with you and rolls around in your brain, long after you've seen it. You can't ask for much more than that in a movie.