I’ll say one thing for “Knock at the Cabin”: M. Night Shyamalan may have made the politest – and the most provocative – home-invasion horror movie you’ll ever see.

The four strangers who show up uninvited at a rustic getaway in the Pennsylvania woods, spouting biblical pronouncements about Armageddon and toting scary-looking homemade weapons (which they call “tools”) do knock before they barge in on Eric (Jonathan Groff), Andrew (Ben Aldridge) and their adopted daughter Wen (an adorable Kristen Cui). And that’s after their leader, Leonard – played by Dave Bautista, in full gentle giant mode, wearing nerdy, wire-framed glass that appear too small for his boulderlike head – has introduced himself to Wen in the front yard, even going so far as to help her catch grasshoppers.

I’m not saying the whole scenario isn’t creepy: Bautista’s imposing, tattooed physique makes for an unsettling contrast to the not-quite-8-year-old Wen’s tiny frame. And when Leonard’s accomplices – excuse me, his “associates” – bust into the house and one of them (Nikki Amuka-Bird) whacks Eric in the head, severely concussing him, she immediately identifies herself as a nurse, offering first aid. What in God’s name is going on here?

God may have a lot more to do with this coming together than it seems. Leonard, a teacher/bartender from Chicago, has been guided here by mystical visions to deliver a prophecy. So have Amuka-Bird’s Sabrina, who came all the way from California; Adriane (Abby Quinn), a short-order cook from Washington, D.C.; and Redmond (Rupert Grint), a Massachusetts gas-company worker who is the only grouch in the bunch. The world is about to end – by tsunami, disease, storm and a blizzard of aviation accidents – unless the residents of the cabin, for reasons that are never explained because they are, quite frankly, cuckoo – sacrifice one of themselves.

Call this unholy quartet, who didn’t know one another until they met in an internet chatroom, the Four Average Joes of the Q-Anon Apocalypse.

From left: Ben Aldridge, Kristen Cui, Jonathan Groff and Dave Bautista in “Knock at the Cabin.” Universal Pictures / PhoByMo

Based on the book “The Cabin at the End of the World” by Paul Tremblay (whose disturbing plot has been softened slightly by Shyamalan and co-writers Steve Desmond and Michael Sherman), “Knock” is satisfyingly atmospheric and tense. It’s also moderately bloody, but the intruders clean up after themselves.

Shyamalan plies our current paranoia here to great effect. To anyone who feels, at times, so overwhelmed by the drumbeat of climate disaster, economic collapse, crime, mass shooting and terrorism, deadly viruses, and political polarization that it feels as the apocalypse is upon us, “Knock at the Cabin” will resonate powerfully.

But there are problems with this story. If Leonard and his crew want to save humanity, they don’t do a very good job of articulating their beliefs to the people they need to convince most, let alone us. With Eric concussed and not thinking clearly, Andrew is the only grown-up in the room who seems to have his head screwed on straight, representing the perspective of the audience: These people are crazy. But Shyamalan clearly invites us to question that assumption, as horrific calamities, seen on the cabin TV, start to pile up. There’s also a suggestion that homophobia may have played a role, for at least one of the four interlopers, in the selection of this particular cabin to terrorize.

Shyamalan keeps things deliberately vague and ambiguous – which actually contributes to the mood of delicious instability – but it’s also frustrating: If Leonard, a teacher, after all, is trying to make the case that he’s not nuts, he’s unsuccessful.

I’m not sure whether that’s a problem or a plus, or maybe both. Bautista is great: Leonard is a desperate, driven and heartbroken man because, as he sees it, he has to commit an unthinkable act – or, rather, force others to commit one – to achieve a greater good. In the end, “Knock at the Cabin” is about the intractability of two powerful human impulses: altruism and self-preservation.

That’s a lot of thematic baggage, maybe even too much, for one home-invasion thriller.