A love triangle that begins online and has dark angles.

“Lover, Stalker, Killer” is a haunting and thought-provoking Netflix documentary about a love triangle gone horribly wrong. I don’t mean it in a comical sense; I mean it in a darker sense. One that introduces us to a psychopath in the mix.

Last week, I panned the spy action comedy Argylle,” one of the reasons being its predictability. It makes me glad it’s not doing much business so far. The following paragraph in this review is based on a true story that I’ve never heard of, so it ended up being unpredictable. And no matter what you’re about to read here, I didn’t give away the most crucial element about the film. “Lover, Stalker, Killer” is really something to view and absorb.

We meet a mechanic named Dave Kroupa, who started a family, but had to split up with his wife Amy, because they weren’t happy anymore. He moves to Nebraska, where he decides to start online dating, and meets Liz Golyar, who runs a cleaning company called “Liz’s Housekeeping Service.” They have a lot in common, especially since they both have kids and love Sci-Fi movies, but it doesn’t last long.

And one day, Cari Farver comes in. She’s a programmer analyst and single mom, whose son is in college. He looks her up on the same dating site, and they have their first date. She’s the kind of person who seems different from the women he’s been dating.

However, when he invites Cari to his place, Liz comes over to grab some things. That’s when these three meet.

It’s only been two weeks since he and Cari are dating, and when he denies her suggestion that they should move in together, she dumps him. At this point, he’s thinking: “No matter how well you hit it off with somebody, you don’t really know who they are.”

This is when she begins harassing him and Liz by text and email. She texts Dave horrible things and says she moved to a place closer to his, while keying Liz’s car and breaking into her house to spray paint the word “WHORE” on her wall.

At this very moment, he and Liz feel safe together enough to rekindle their relationship. That is until this psycho burns down her house, forcing Dave and Liz to move away but in separate places. But this doesn’t end her reign of terror.

Then, the movie shifts over to an examination of Cari, who has been diagnosed with bipolar disorder, which would ultimately lead to her unacceptable behavior and disappearance. Or maybe it’s not what it seems.

The only way the story would probably be predictable is if it were made into a feature film, unless it was written with ingenuity. But I’m not giving out any ideas; I’m praising “Lover, Stalker, Killer” as one of the most entertaining docs of the year. I may not be able to grab every detail in the story, but I caught enough to convey its difference between the good and bad characters. Director Sam Hobkinson (“Fear City: New York vs the Mafia”) presents this hauntingly true story in an informative manner.

For those of us who have never heard of this true story, we’re kept at the edge of our seats (chairs and coaches), and we’re seeing the character examinations here. And even if you have heard of this story, you still should see how well edited it is. I’m just glad I took a break from online dating.

Streaming on Netflix