The Sixth Commandment is a new four-part drama for BBC One that's set to enthral viewers with its unsettling web of murder and lies.
But while the plot of the series may seem outlandish to those not familiar with the story, the drama is actually based on a true crime case.
Here's all you need to know about the strange but true story behind The Sixth Commandment.
When is The Sixth Commandment on TV?
The four-part series begins tonight (Monday, 17 July) at 9pm on BBC One.
Viewers can see the story continue in episode two on Tuesday, 18 July at 9pm, and the third and fourth episodes will air on Monday, 24 July and Tuesday, 25 July at 9pm.
What is the true story The Sixth Commandment is based on?
The series follows the horrifying circumstances surrounding the deaths of Peter Farquhar and Ann Moore-Martin in the village of Maids Moreton, Buckinghamshire.
Farquhar was a novelist and English teacher whose career had included teaching at Manchester Grammar School and Stowe School, but while lecturing at Buckingham University, he crossed paths with Ben Field.
Despite Farquhar being in his sixties and Field in his twenties at the time, they began a romantic relationship and even had a betrothal ceremony at their church in 2014.
Farquhar changed his will to make Field the main beneficiary and even made him his literary agent, with no clue that Field was in fact poisoning him by drugging cups of tea.
Some of the drugs used also left Farquhar questioning his sanity in an extreme form of gaslighting, and he passed away in October 2015 with his death initially being recorded as accidental.
Timothy Spall, who plays Farquhar, said: "It isn't a standard gaslighting story where you see the victim as a pawn. This is much more sophisticated.
"You're talking about deeply intelligent people who are hoodwinked by their own dreams being answered, the softest part of their souls are being touched by somebody so seemingly genuine."
However, Field's disturbing actions in the sleepy village continued as he then set his sights on Farquhar's friend and neighbour Ann Moore-Martin, a former head teacher in her eighties who allowed Field to move in with her when he claimed he had nowhere to go.
She began signing over large amounts of money to him after he claimed his brother was in need of a dialysis machine to be able to continue his studies at Cambridge, and also changed her will to include Field who she was in a relationship with.
But when Moore-Martin began to get ill in late 2016, her niece was suspicious and called the police – who made a link with Farquhar's death and realised Field had been drugging her, too.
Moore-Martin was able to change her will to remove Field, but died of natural causes in May 2017.
The Sixth Commandment's writer Sarah Phelps said: "It felt like one of those Hans Christian Andersen or The Brothers Grimm fairy tales which everybody thinks are really cute but they're not - they're terrifying.
"I felt that there was something quintessentially English in this dark, dark fairytale in the sense that you could live in this ordinary place, where everybody knows you, you’re surrounded by good neighbours, and yet you could slowly die in front of them and nobody would know what was happening or say anything."
Who stars in the series?
Spall stars as Farquhar and said: "It’s a massive responsibility when you're playing a real human being who was a family man, as they live on with love in people's hearts.
"It’s never lost on me and I have done my very best for Peter. I'm not trying to make it sound like some worthy, noble thing, but you're telling a story about someone who's loved and remembered and was alive not that long ago. So you really do want to get it right."
He's joined by Anne Reid as Moore-Martin, who said: "What's terrifying about this story is that this sort of terrible evil is hiding in plain sight. Ben Field could be anybody – he feels like he's a normal loving guy.
"It makes you sort of question your own life. It's very difficult to judge relationships. Often you look at other people and you wonder ‘Why are they attracted to each other?’"
Éanna Hardwicke plays Ben Field.
The cast also includes Sheila Hancock as another neighbour Liz, Annabel Scholey as Moore-Martin's niece Ann-Marie Blake, and Jonathan Aris as DCI Mark Glover.
Aris said: "The crimes themselves are so extraordinary and Ben Field’s character so bizarre and ghastly that they almost defy dramatisation - if it wasn’t true, you wouldn't believe it."
What happened to Ben Field?
Field was eventually arrested in January 2018 and found guilty of Farquhar's murder in August 2019.
He was sentenced in October 2019 to life in prison with a minimum of 36 years and has lost two appeals against his conviction.
Hardwicke, who plays him, said: "The judge described him as someone who had a pathological need to manipulate, hurt and have power over others. He gets a thrill from lying and playing a part well, whilst fooling everyone, which he pretty much did.
"I think he himself said that what interested him was putting on a good performance."
The Sixth Commandment begins tonight (17 July) at 9pm on BBC One.