I’m not a huge horror buff, fan or aficionado. But when I sit down to watch one I do like for it to be smart.

“Clock” is a childbirth/”biological clock” thriller that has modern medicine playing God, The Holocaust and Human Evolution itself as its subtexts.

Smart? Writer-director Alexis Jacknow’s debut feature borders on brilliant.

Dianna Agron plays Ella, our protagonist, a 37 year-old doctor’s wife whose interior design business is just blowing up, so she’s just a tad touchy if not downright testy when her pregnant-or-already-a-mother girlfriends gang up on her at a friend’s baby shower.

Wanna feel the baby kick? Erm, no.

“It’s a BABY, Ella, not an ALIEN.”

Their “Don’t worry, your biological clock will kick in” assurances fall on deaf ears. She’s not sure she has one. Especially with her aged, widowed father (Saul Rubinek at his nudnik best) badgering her about the family that almost didn’t make it through the Holocaust, a genetic line that “ends with you” if she doesn’t ante up.

Her new OB-GYN is quick to turn her “I don’t think I’m ready yet” upside down with the news that womb-wise, she’s now officially “geriatric.” But there’s this “clinical study.”

Ella gives it some thought, notes the friction it’s causing in her otherwise happy/sexually-fulfilling marriage (Jay Ali plays her husband) and rashly cancels her biggest-ever contract, tells her husband she’s got business out of town and submits to the pills and “cognitive therapy” of Dr. Simmons, played by Melora Hardin of TV’s “The Office” and “Transparent.”

Let’s get that “clock fixed,” the good doctor says. Side effects? Of course. This is a horror movie, after all.

Ella gives Agron a character with edge and just a whiff of vulnerability, and she is fierce and frightening in the part. Ella pushes back against pushy parent and pushy friends, snaps at the good doctor and Agron lets us see hallucinations she pretty much shrugs off because this broad is tough. It’s a terrific performance.

A funny moment — Ella sees a tree-climbing child whose distracted mother hasn’t noticed and then distracts her with more kvetching about “You WANT a baby!” Mom’s one-track-mind lobbying means no one intervenes and the kid takes a terrible fall.

Stephen Lukach’s unsettling score, the gloomy-doomy production design of Kristin Gibler and Jacknow’s lean script and focused direction build the mood, so that when this “Let’s get you pregnant” picture turns dark, we’re braced for it.

The veteran character actor Rubinek brings an alarmingly cruel edge to this needy aspiring grandad, leaning into “type” and crossing several lines as he guilts his daughter with “Your mother and I loved each other THAT much” (a dig at the husband, sitting right next to Ella) and launching into a lecture that includes “the camps (Bergen-Belsen)” and decrying the “empty chairs at the table” because Ella hasn’t been fruitful and multiplied.

“Evolution” and “procreation” seems to be on everybody’s lips. It’s no wonder our Ella is ready to go off the deep end.

Nightmarishly gory visions of childbirth rattle her. Drugs and an isolation tank and Rorsach tests that animate suggest that she’s got good reason for doubts.

Frights? There are a couple. But this is mostly a thriller about Ella, a surrogate for generations of women, battling against peer pressure, family pressure and the politics of stealing a woman’s bodily autonomy, fighting to live her best life, one that she chooses, one that won’t include a baby.

Rating: unrated, violence, gore, sex, nudity, profanity

Cast: Dianna Agron, Melora Hardin, Jay Ali and Saul Rubinek.

Credits: Scripted and directed by Alexis Jacknow. A 20th Century Studios/Hulu release.

Running time: 1:31