It’s important to know when to “drop the mike.” Know when to say “when,” don’t spoil a peak moment by trying to top it, and don’t clutter up your finale so badly it spoils the effect of the stand-up set, concert, play, series or movie thriller that came before it.

“Mother’s Day” is a mean, implausible and formulaic kidnapping thriller, a distaff Polish “Taken,” in which the bad guys have grabbed the son of a woman with “particular skills,” and a chip on her shoulder.

It hits many of the standard plot points, serves up visceral violence in many settings and even has our heroine engage in a bit of self-surgery, a staple of the genre.

A nice twist? Her stolen son (Adrian Delikta) doesn’t know this demon who stabs, punches, torches and shoots her way to him is his birth mother, even if the bad guys do. Because that’s why they took him.

“Mother’s Day” could have been an exciting if wholly predictable thriller of the “bad movie worth recommending” persuasion. But director Mateusz Rakowicz and co-writer Lukasz M. Maciejewski make such a hash of the bits after the climax and beginning of the credits that they strip a lot of that goodwill away.

Agnieszka Grochowska (“How I Fell with a Gangster”) stars as a supposedly dead-and-buried deep cover agent, high-mileage and low on patience for Poland’s malefactors — be they Proud Boys (she pummels a pack of them with a SIX PACK OF BEER in the opening scene) or mobsters.

“Sorry ma’am, but these days, if someone doesn’t hit a girl, he’s a sexist.”

The bad guys fight back, of course.

When she was made to disappear, her son Maks (Delikta) was adopted out to strangers who knew nothing of his family history. But she stalks him online, checks in on him from a safe distance and grudgingly accepts her fate and his.

And then this Serbian’s goons grab the kid, “revenge” for something she had a hand in long ago. No matter what her handler (Dariusz Chojnacki) tells her, she’s going to retrieve him. Give her the barest intel, and the psychotics hired to do this kidnapping will rue this “Mother’s Day.”

Good fight choreography, camera placement and editing can turn anybody into a gang-burying badass, and Grochowska is just credible enough — on the sliding Gena Rowlands (“Gloria”) to Angelina Jolie (“Salt”) scale — to make this work.

A sizzling set-piece set in a kitcenh has the bad guys basically stand back and wait until she picks up two eggs and proceeds to bust those eggs, bust heads, pick up a knife, a frying pan, a wok filled with flaming oil and a meat tenderizer to make her impatience with their nonsense known.

The villains, chiefly Szymon Wróblewski as a “Borat” underweared (suspenders and a banana hammock) psychopath and a brutish Russian intel commisar labeled “The Witch” (Jolanta Banak) are outstanding.

But the mother-son scenes have a dreary predictability that let us know exactly what is coming, when and in what order, the moment he asks “Who ARE you?” (in Polish with subtitles, or dubbed) and she replies “I am your ONE chance!”

And then, another layer of goodwill is stripped away with all the nonsense shoved into the finale and closing credits.

Rating: TV-MA, graphic violence, nudity, profanity

Cast: Agnieszka Grochowska, Adrian Delikta, Dariusz Chojnacki, Konrad Eleryk and Szymon Wróblewski

Credits: Directed by Mateusz Rakowicz, scripted by Lukasz M. Maciejewski and Mateusz Rakowicz. A Netflix release.

Running time: 1:34