Ma (2019) doesn’t need to spike your drink to put you to sleep.

The most horrifying thing about this lukewarm all-filler, no-killer thriller is how much on-screen talent is wasted in telling its flaccid, predictable and profoundly stupid story.

When Maggie (Diana Silvers) is moved back to her mum’s hometown, she’s quick to make new friends and starts hanging out with them outside the local liquor store, hoping to get a sympathetic adult to buy them some booze. Enter Sue Ann (Octavia Spencer), a veterinary nurse who agrees to help the kids out providing they promise not to do anything dangerous. Quickly gaining their trust by repeating her booze-buying, she invites them back to party in her basement, where she can be sure they won’t endanger themselves but Ma has some dangerous plans of her own.

Every horror story relies on the title characters making bad decisions at some point, but “Ma” relies on its otherwise smart and, refreshingly, generally likeable kids being so unbelievably gullible and willfully stupid that any possible tension just evaporates like spilt vodka.

Octavia Spencer does her best to be menacing and her performance is solid but she’s trapped in a script which allows her character to behave and act with such utter impunity that nothing really seems to matter.

Given the film was originally written without providing any backstory to “Ma” and one was hastily retrofitted to the story, it’s a real shame that the backstory provided just raises more inconsistencies and questions, not only around Ma’s actions and her targets (there’s a conspicuous absence on her revenge list) but also make it feel like this Ohio town has, like, five families living in it. Stuffed with narrative dead-ends and weirdly dangling plot threads, the film only manages to amuse a couple of times, notably when Ma pulls a ‘Driving Miss Crazy’ stunt unexpectedly.

Luke Evans, Allison Janney and Juliette Lewis are big names in small roles that get very little to do and while Diana Silvers may impress in “Booksmart”, she just disappoints in this DrinkDumb teen horror misfire.