Murder, pedophilia, blackmail and morbid obesity figure into the plot of “Wade into the Water,” an odd and intriguing debut feature from director Mark Wilson and screenwriter Chris Retts.

It’s “Taxi Driver” meets “Napoleon Dynamite” — a quirky, dark mystery-thriller. And it’s a poster movie for the genre known as “Film Festival Movies,” as in distributors wouldn’t rush to buy it because “What theater would book it?” or know how to advertise it.

Veteran bit player Tom E. Nicholson plays our grumpy loner “hero,” an overweight giant in tent-sized shorts, beard and glasses. And when we meet him, he’s wheezing, covering his face in a mask and his head in a hoodie, pulling out a pistol and breaking in.

Our unnamed protagonist is a work-at-home medical billing specialist, alone save for his pet guinea pig and his TV, where he consumes a steady diet of free TV old movies. He has a “usual” at the local Chef Burger, a bad temper and a court-ordered shrink that he’s got to see about that.

But the thing that triggers that opening breaking-and-entering is a misdelivered piece of mail. It’s a DVD. And on it, child pornography.

For reasons he doesn’t reveal at first, our plump dyspeptic digs into who that disc was intended for and what sort of “monster” that person might be.

Every transaction in this guy’s life, from mental health center receptionist to the fellow who serves him his burgers to a mail clerk to the fellow behind the counter at the gun shop, is fraught. We never know what will set our man off, even if we know his four favorite profanities.

“Gun shop,” you say? Why yes, there’s that “Taxi Driver” thriller element here, remember.

“What’s it for?” “What the f–k does THAT matter?”

And that’s what throws him in the path of the strange young woman named Tilly (Danika Golmbek, odd and interesting).

Retts’ script has edge, a hint of blackmail and perversion and guilt and a troubled past for these two to talk about, or around.

But the center of this, its core appeal, is in Nicholson’s low-grade irritation at life, how every little thing — just getting in and out of a compact car, just getting his burger the way he likes it — is maddening.

Whatever made him this way might be what he wants the gun for, after he’s done his detective work — approaching possible victims of a pedophile, narrowing down his options, avoiding “the cops.”

And the girl? She’s no slouch as a gumshoe herself.

“Thriller” doesn’t quite fit here, because no matter what the stakes, nobody seems that worked up about them. It’s more disquieting than fun, but more amusing than troubling.

And Nicholson makes this Incel life of quiet, slovenly desperation fascinating to look in on, if not embrace.

MPA Rating: Unrated, violence, profanity

Cast: Tom E. Nicholson, Danika Golombek, Samuel Whitehill

Credits: Directed by Mark Wilson, script by Chris Retts. An Indie Rights release on Amazon Prime, Tubi TV.

Running time: 1:28