'Black Mirror' fans say 'Loch Henry's' ending is the 'biggest twist of the season'

"Loch Henry," the second episode of the sixth season of "Black Mirror," has the elements of a ghost story. Have you heard of the story of Iain Adair? Based on what happens in the plot, the characters probably wish they hadn't.

Pia (Myha’la Herrold), an American woman, travels to her boyfriend Davis' (Samuel Blenkin) Scottish hometown to meet his mother and to film a documentary.

Pia is stunned that a town this beautiful could be so empty. Turns out this wasn't always the case, as Davis' friend Stuart (Daniel Portman) reveals. The atrocities that occurred at the hands of Iain Adair scared away the once plentiful tourists.

After hearing the story in all its gruesome detail, Pia thinks they should shift focus and film a documentary about that instead of their original idea (which was about a man who steals eggs and no, we're not kidding).

At first, Davis is hesitant to move forward: His father, Kenneth, a policeman, had been killed by Iain ... sort of. Kenneth was shot in the shoulder after visiting Iain's farm. In the hospital, he contracted a MRSA infection and died. Davis was only 8 at the time. His mom, Janet (Monica Dolan), has never let go of the pain.

After starting on the project, Davis uncovers his personal connection to the case is far deeper than he ever could have realized.

Online, fans have reacted to the episode's turns with shock. "The episode has the biggest twist of the season," one tweet reads. Another deemed it has the "saddest ending ever." The consensus is, "Another 10/10 for 'Black Mirror.'"

What did Iain Adair do, supposedly?

In Stuart's succinct words, he "tortured and killed people." Iain's crimes were uncovered due to a high-profile disappearance that took place in 1997.

Dawn and Simon Challis, a couple in their 20s, arrived to Loch Henry for their honeymoon. A week into their trip, they disappeared. Once a major news story, Dawn and Simon's disappearance was eclipsed by Princess Diana's death.

Iain Adair was drinking in Stuart's father's bar and acting strangely. Stuart's father, Richard (John Hannah), asked Kenneth, a policeman, to check on Iain. From the upstairs window, Iain shot Kenneth in the shoulder. Then, he shot his mother, father and himself.

In the cellar, investigators uncovered "a torture room," Davis says.

"This guy had been abducting people, keeping them down there for weeks at a time. Then burning the bodies out in the fields," Davis says. Stuart adds that the crimes were also of a sexual nature: "Really extreme stuff."

The honeymooners were among multiple victims. The rest were hikers and travelers thought to be victim to Scotland's unforgiving landscape (more on that later).

The twist makes things a lot more complicated

At Pia's urging, Davis agrees to make a documentary about Iain Adair. They even get Davis' mom Janet to agree to make a film.

Stuart, Davis and Pia travel to Iain's lair and see the vestiges of his crimes — blood splatter so saturated even Dexter Morgan would have been stumped.

On their way home, Davis, distracted, gets into a car crash (they're relatively all OK, despite it being a head-on collision). At the hospital, Davis sees Richard, who is there for a fall.

He had been urging him to stop investigating Iain. Davis learns why at the same time Pia, alone with Janet, discovers the truth as well.

Pia, alone in Davis' room while he's in the hospital overnight for observation, watches footage for their documentary. One of Davis' parents' old VHS tapes, all containing recordings of their favorite detective show, starts playing.

Then the footage switches to something else recored over the TV show. Kenneth is with Iain near the couple, who are tied up. There it is: Proof that they were in on it together. Then, they introduce Janet — who, wearing a red Venetian mask, runs towards the couple with a drill. "The mistress is going to have fun with both of you. How does that sound?" Kenneth, narrator from hell, says.

What happens to Pia, and how does she die?

Pia does not play things cool, which leads to her downfall. After she realizes Janet's involvement in the sickening murders, she, respectfully, begins to glitch. Then, she sees the scarlet mask hanging up on the wall of the living room — proof that Janet committed atrocities and is proud of them.

Unable to stomach having dinner with known killer Janet McArdle, she heads to the bathroom to gather herself, then runs out of the house.

Janet, suddenly suspicious of Pia, walks upstairs and sees the VHS in question.

She gets in her car and tracks Pia down, trying to coax her back inside. "I won't hurt you," Janet says, despite having lost her credibility to say anything like that.

Pia, repelled, runs away. She leaves her excellent hiding spot behind and wall and heads toward the river.

There, Stuart's foreboding comments about Scotland's landscape come to fruition. She trips on a rock, hits her head on her way down and dies.

Clues for the ending were there all along

Janet takes her own life. Before she does, she gathers all the video evidence of her crimes with Kenneth and Iain, and the polaroids taken with victims (Polaroids!). She leaves a note: "For your film. Mum."

Turns out Kenneth had killed Iain and his parents, then deliberately wounded himself to frame Iain.

Just like the VHS tapes was on the shelves and Janet's mask was on the wall, Janet never really hid her secret. Seen through a different lens, her one-off comments are all quite ... obvious.

Janet's rant, which she gives after Davis asks her permission to make a documentary about Iain Adair, is especially telling.

"My Kenny died because of that man. If Iain Adair were still alive I'd wring his neck with my hands. We were happy, before he broke it all. Ruined it all. Such a stupid man. Just the waste of it," she says.

At first, it seemed like she's speaking about her marriage. In light of the VHS tapes, it's clear she was speaking about their sick Ménage à trois.

Then, when she's being filmed for the documentary, she says the last time she was filmed was with Kenneth's camera. "But your dad never had all this stuff," she says.

"He wasn't filming for broadcast," Davis replies.

"Can you imagine?" Janet says, joking to herself — a joke only she understands.

Is Loch Henry based on a true story?

No, but there is a meta twist. "Loch Henry" seems to be a commentary on the true crime genre — which is responsible for many of Netflix's biggest hits — and how it further victimizes its subjects, as critics of "Dahmer" said.

Pia and Davis set out to make a true crime documentary but then become the subjects of an award-winning documentary called "Loch Henry: Truth Will Out," with a dramatization on the way.

The town benefits from the documentary's popularity, as Stuart predicted. In the background of his now popular bar, tourists wear red masks like Janet's.

"Loch Henry" wins a BAFTA. Davis is praised by the documentarian during her acceptance speech, but seems uncomfortable with his role in the content machine. Instead, he seems broken by the loss of Pia, the revelations about his parents and overexposure. Staring at the statue of the award he's just won, it's as if all he can see is his mother's mask.

This article was originally published on TODAY.com