The premise of Blumhouse’s new kick-off-the-summer scare show, Ma, is frankly kind of ridiculous. A group of teens in some Midwest Nowheresville, including recent California transplant Maggie (Diana Silvers), are hanging outside the local liquor store trying to persuade an adult passerby to go in and get beer for them when they meet Sue Ann (Octavia Spencer). Initially hesitant, she eventually takes a liking to the little scamps and agrees to grab them what they want. Furthermore, she even invites them back to her secluded house in the woods to party in her basement so they don’t have sneak around outdoors and hide from the cops (even though they all seem to have somewhat absent parents and could theoretically just drink in one of their own basements?). This sounds totally normal and cool, right?

And yet somehow, from this incredulous scenario, writer Scotty Landes and director Tate Taylor spin a fairly natural and organic thrill ride that steadily allows its teen protagonists to become believable entrenched in. When first presented with this newfound party scenario, one of the kids, Darrell (Dante Brown), automatically says, “No. We don’t know this lady,” which is absolutely the correct response. But since Sue Ann is so kindly and works at the local veterinarian hospital, what could be the harm? All she seems to want is to provide a space for them to have a good time responsibly. Soon enough, everybody’s calling Sue Ann “Ma” and her basement becomes the hippest party venue amongst the entire local high school population.

Of course, it goes without saying that Ma’s intentions are not all that benign and dark secrets from her past are going to have very real implications to go along with her new party queen status. This is where Octavia Spencer comes in.

As the movie’s chief strength, Spencer doesn’t just play Ma as your typical horror movie psycho. She makes Sue Ann into a fully realized human being, scarred from a life of trauma that stems all the way back to her own teenage years and finally being let loose in unpredictable ways. It’s a hypnotic performance, going from amusingly strange to achingly heartfelt to seriously disturbed, sometimes all within the same scene. No matter how offside and desperate Ma’s behaviour becomes (not to mention her unnerving command of Instagram stories), Spencer makes sure we still feel for her.

The movie itself doesn’t always live up to the Ma at it’s core, burdened somewhat by that generically contemporary Blumhouse aesthetic and unwillingness to really parse through the more troubling aspects of its narrative, including a late revelation that could have been more interestingly handled. For his first foray into horror after shifting away from helming prestige dramas, Taylor knows how to go through the motions but never really makes the movie his own. It’s still Jason Blum’s world and the directors (with the exception of a few cases) generally just play within it.

But Landes’s script continually surprises by gradually building momentum and twisting in new directions just when it seems the story is about to run out of gas. By the time the explosive finale hits, you may be shocked at how invested you are. Also refreshing is the teenage dialogue, which, for the most part, actually sounds like how real kids interact, while putting a much-needed perspective on the female coming-of-age experience. Meanwhile, Taylor gets great support from Juliette Lewis and Luke Evans as a couple of the parents who are gradually revealed to have their own level of culpability in this entire situation.

For a movie that constantly seems on the verge of falling apart, Ma ends up delivering a well crafted and consistently entertaining horror funhouse.