Honestly, if recent media has taught us anything, it’s that maybe we don’t need complete honesty from our partners. From the true crime documentary Should I Marry a Murderer? to The Drama, it seems that knowing the worst things your partner has done doesn’t always lead to a healthy, loving relationship… just a thought.
Yep, we’re back with another Netflix documentary. From Louis Theroux's Inside the Manosphere to Trust Me: The False Prophet, true crime on this streaming platform never disappoints. But despite all the recent successes on Netflix, nothing has quite captured social media’s attention like Should I Marry a Murderer?
Life looks pretty different now.
The three-part documentary, directed by Josh Allott, follows forensic pathologist Dr Caroline Muirhead, who discovered that her fiancé, Alexander “Sandy” McKellar, had taken another man’s life just a few years before they met. It’s a wild ride, and the true story behind Should I Marry a Murderer? has people hooked – as well as its rather enthusiastic use of Snapchat filters.
- Is Should I Marry a Murderer? a true story?
- How did Caroline and Sandy get together?
- What happened in Should I Marry a Murderer?
- What is the true story behind the death in Should I Marry a Murderer?
- Were the McKellar brothers suspects in Parsons death?
- Why did Muirhead stay with McKellar after the incident?
- What’s missing from Should I Marry a Murderer?
Is Should I Marry a Murderer? a true story?
I know, I know, it’s a literal documentary series. But the events are so extraordinary, and so interwoven with social media vlogs, that some viewers briefly wondered whether it was scripted. In fact, even director Josh Allott had a similar reaction at first.
"When I first heard Caroline Muirhead’s story, I thought this must be the plot of a drama, not the real experiences of a living person," Should I Marry a Murderer? director Allott said in a statement via Netflix. "Her dilemma is so unimaginable, but it’s also one that’s impossible not to hypothesise in your own relationship. The person you’ve just said you’ll spend the rest of your life with tells you that they have a terrible secret. Do you choose to keep that secret and live with the awful consequences, or reveal it, and destroy the person you love and everything you’ve hoped for?"
It's a true story, told from the whistleblower herself.
How did Caroline and Sandy get together?
In 2020, Dr Caroline Muirhead was a 32-year-old pathologist working in Glasgow who had recently gone through a difficult breakup. She met 31-year-old Alexander “Sandy” McKellar on Tinder, and the pair connected almost immediately. They quickly began spending most of their free time together, with Muirhead driving out to the estate where McKellar lived and worked as a gamekeeper.
The relationship progressed rapidly, with the pair soon spending almost all of their time together. Just two months later, McKellar proposed and Muirhead accepted. Her friends and family were shocked, particularly as many of them had not yet met him.
What happened in Should I Marry a Murderer?
Following the engagement, Muirhead asked McKellar whether there was anything she needed to know before they got married. He appeared nervous, so she asked if he had children or any other major secrets.
McKellar then told Muirhead that he had a “horrible” secret. “Then he told me what he’d done… something that he’d got away with for years,” Muirhead said. “I was in shock, frozen almost. I didn’t know what to believe. This man I thought I could be with for the rest of my life had just told me he was a killer. I didn’t know what to do.”
Muirhead reveals that three years earlier, while driving under the influence, McKellar had hit a man. Not only did the victim die shortly after the accident, but McKellar then concealed the body with the help of his twin brother, Robert. Muirhead describes being completely stunned by the confession.
She later reflects in Should I Marry a Murderer?: “[To have your fiancé] say to you, ‘I’ve done a horrible, horrible thing,’ [it’s] something so vile it flips your entire world upside down. To remain in love, you have to keep this secret that you know is going to destroy you. But if you reveal it, then you destroy everything.” She then turns to camera and asks, “I mean, what would you do?”
What is the true story behind the death in Should I Marry a Murderer?
On 29 September 2017 — three years before McKellar’s confession to Muirhead — he was driving through the Scottish Highlands with his twin brother, Robert. McKellar had been drinking heavily after dinner with his hunting group at the Bridge of Orchy Hotel and was speeding late at night on rural roads.
That same evening, former Royal Navy officer Tony Parsons was undertaking a charity cycling tour in aid of prostate cancer awareness. The 63-year-old grandfather and father of two was attempting to complete a 100-mile ride through Argyll and Bute in one go. He stopped briefly at the hotel for a coffee before continuing on his route, despite worsening weather conditions and heavy rain.
Shortly after 11 pm, the McKellar brothers struck Parsons with their Isuzu pick-up truck on the A82 near Bridge of Orchy.
The incident did not end there. Parsons was still alive following the collision, but instead of immediately calling emergency services, the brothers moved him to a more secluded location while they returned home to change vehicles. He later died from severe blunt force trauma, with rib fractures likely restricting his breathing. It is believed he survived for approximately 30 minutes after the initial impact.
The cold case solved by a Red Bull can.
After the collision, the McKellars drove back to their home on the Auch Estate near Tyndrum. They later returned to the scene in a different vehicle, retrieved Parsons’ body along with his bicycle and belongings, and buried him in a peat bog on their private land used for disposing of dead animals. His bicycle was hidden behind a nearby waterfall and never recovered.
The brothers also destroyed Parsons’ phone and SIM card, burned his wallet and helmet, and disposed of further evidence related to the crash. McKellar later took the damaged vehicle to be repaired, telling mechanics he had struck a deer.
Were the McKellar brothers suspects in Parsons death?
The McKellar brothers believed they had gotten away with the crime, even as a search for Parsons began. Then, almost a year later in August 2018, the Scottish police received an anonymous letter urging authorities to “pay attention” to the McKellar brothers. Both were questioned, but investigators found no evidence linking them to the incident, and the lead could not be pursued further.
The case remained unresolved until November 2020, when McKellar confessed the full story to his fiancée, even revealing that she had been close to the burial site without knowing it. “We went to bed and he cuddled in next to me and fell asleep,” she later recalled to the BBC (via The Scottish Sun). “I was wide awake and on my phone trying to Google anything about a missing cyclist to see if this could be true and then I saw the appeals about Tony Parsons.”
Muirhead asked McKellar to show her the gravesite. While there, she discreetly dropped a can of Red Bull as a marker in the woods, planning to use it later to help direct police to the location.
It wasn’t until 27 December 2020 that Muirhead formally reported McKellar to the authorities. She has said she spent the intervening weeks gathering further information about him, including confirming details about where Parsons’ body had been disposed of.
Following her report, both McKellar brothers were brought in for questioning, and acting on Muirhead’s information, Parsons’ body was recovered by police in January 2021.
Three years later, the trial finally took place. Robert McKellar pleaded guilty to covering up the death and was sentenced to five years and three months in jail. Alexander McKellar also pleaded guilty to culpable homicide and was sentenced to 12 years.
Why did Muirhead stay with McKellar after the incident?
McKellar and his brother remained living with Muirhead after the initial police questioning, unaware that she had already reported them to the authorities. Even once this was revealed, the couple had a fierce argument, but Muirhead ultimately moved back in with him on the estate while police continued gathering evidence.
This detail has clearly unsettled viewers, judging by reactions across Reddit threads and TikTok discussions. However, it is also difficult to fully comprehend what you might do in the same situation, given the intensity of the emotional and psychological conflict involved.
“There is something deeply relatable about staying in a relationship that you know is bad for you, and Caroline was determined to own these mistakes as a lesson to others who might ever be caught in a similar situation,” Should I Marry a Murderer? director Josh Allott said in a press statement.
What’s missing from Should I Marry a Murderer?
The Netflix documentary is told largely from Muirhead’s perspective, meaning significant parts of the victims’ stories and wider context are not fully explored on screen. For those wanting a broader view, viewers are encouraged to watch the BBC documentary The Vanishing Cyclist, which aired in August 2025.
Additionally, some critics have argued that the McKellars’ difficult upbringing is underexplored in the series. While the show does briefly allude to their past, including a specific incident in which their father was previously charged with weapons offences, alongside some contextual input from residents of their hometown, it doesn’t really delve much deeper into their background or formative experiences.
A cold case solved by a confession between fiancées.
The production also notes that both Police Scotland and Victim Support Scotland declined to participate in the documentary, meaning their official responses to Caroline’s claims of investigative shortcomings and lack of support are largely absent from the narrative. As a result, viewers are left with limited insight into why she was not, at the time, reportedly offered more substantial victim support or mental health intervention. They maintain they gave her “appropriate support.”
Furthermore, what is not included in the documentary, however, is that she was allegedly told at the last minute that cameras from an upcoming BBC documentary would be allowed in court, something which caused Muirhead to panic and leave without giving testimony.
Watch Should I Marry a Murderer? on Netflix
