When it comes to what scares us, believing is seeing.

It’s what fuels our modern viral nightmares, like in the case of the kids who don’t know better and their subsequently frightened parents (Nick Allen is an Assistant Editor at RogerEbert.com and is a member of the Chicago Film Critics Association. Though these are the only moments that the film is disorienting—progressively revealing how evil these young girls were—they also make it more tedious.

What kind of monster are we dealing with here: a supernatural reckoning? In the case of a woman named Marina (Daniella Pineda), Mercy Black was the reason that she and her friend Rebecca did a horrific thing to a third friend 15 years ago.In the opening sequence, we see her and Rebecca walk a third girl through an open field (singing “Itsy Bitsy Spider,” so you know it’s ominous) to a ravine, where the third girl is hit in the head with a rock.

Or is this flesh-and-blood slasher justice, like the hook man unleashed on those negligent ‘90s teens in “Egerton is very particular in how we learn about Marina's incident, flashing back to it with abrupt cuts and visual triggers.

When it comes to what scares us, believing is seeing.

But if having their own Momo is Netflix’s latest attempt to grab viewers, they’re gonna need a much more disturbing monster.Years after the event, as a mortified Marina leaves psychiatric care to stay with her sister Alice (Marina meanwhile is haunted by recollections of the crime (as if she didn't work on them just a tiny bit at a facility overseen by Janeane Garofalo's exposition-spewing Dr. Ward). While treading through the mystery of its past and experiencing the supernatural shenanigans of the present, you wait for “Mercy Black” to make you afraid of its secrets. It’s in these passages that Pineda does solid emotional work, showing a woman working through a personal horror. The origin of the song is unknown, but it was first published in 1920 as a song for adults.

What kind of monster are we dealing with here: a supernatural reckoning?

But the limited script by writer/director For a story built on the palpability of belief—that believing in something is more powerful than fact—"Mercy Black" toes a line of practicality with its terror.

The drama is sporadically curious, but you’ve seen the spooky stuff within "Mercy Black" more than a few times before: a creaky old home that conveniently doesn’t have a lot of lighting at night, jump scares that are telegraphed by obvious edits and music cues, a haunted-looking young boy. It’s what fuels our modern viral nightmares, like in the case of the kids who don’t know better and their subsequently frightened parents ( Marina tries to help him by sharing her trick for sanity—saying to yourself that it’s not real, and counting to five—but ‘sounds like Mercy’s back, and Marina better retrace her steps from 15 years ago. ... Marina and Lily, walking across a field singing “Itsy Bitsy Spider”. That moment never arrives.

But it doesn’t feel like Marina’s memories are coming together so much as a writer/director is withholding information for the sake of creating dread, slowly bringing us to his big picture. Even the design of Mercy herself leaves you hoping for a little more menace. The drama is sporadically curious, but you’ve seen the spooky stuff within “Mercy Black” more than a few times before: a creaky old home that conveniently doesn’t have a lot of lighting at night, jump scares that are telegraphed by obvious edits and music cues, a haunted-looking young boy. While treading through the mystery of its past and experiencing the supernatural shenanigans of the present, you wait for “Mercy Black” to make you afraid of its secrets. Though these are the only moments that the film is disorienting—progressively revealing how evil these young girls were—they also make it more tedious.