Netflix's spine-tingling psychological chiller Baby Reindeer has soared to the No. 1 spot - and pretty much everyone is talking about it.
Unlike many streaming service bangers, however, it isn't just the stellar cinematography, top-notch acting or startling plot-twists that has left viewers completely and utterly hooked on this seven-part hit.
No, it's the fact that it is based entirely on the real life experience of Scottish comic Richard Gadd, who plays the central role of himself in the production.
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And if you've seen the show already, you'll be more than aware that one question about the unnerving true story that has apparently has audiences in a chokehold is, 'Why did Martha sign off all her emails 'Sent from my iPhone'?"...
If you need catching up on what this harrowing hit - and real life story upon which it is based - is all about, allow me to fill you in.
Limited series Baby Reindeer follows the torturous tale of a writer and comic's warped relationship with a middle-aged woman - named 'Martha' in the show - who becomes his stalker after they meet at the pub in which he works.
After the obsessive Martha gets hold of his contact information, she bombards him with increasingly terrifying messages day and night.
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All of these emails end in those five unsettling words (or sometimes just 'iphon'), despite the fact that Martha wasn't emailing from an iPhone - nor does she even have one.
The real-life Richard received over 40,000 emails, 740 tweets, 350 hours of voicemail, 100 pages of letters and 45 Facebook messages from the woman in question, but was unable to act after police refused to help.
Gadd has never named the real-life Martha, nor revealed what happened to her.
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When Variety asked if he was concerned about his stalker contacting him following the show's success, he said: "Due to where things ended in real life, it’s not a concern for me."
There are a number of unanswered questions that Baby Reindeer viewers have about the real life stalker's intentions.
In particular, many are baffled as to why she signed off each email in this bizarre way.
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With that in mind, a chartered psychologist has this week lifted the lid on this mystery.
Speaking to LADbible, expert Dannielle Haig explained that the 40,000 emails - all bearing this signature - are 'testament not only to her obsession with Donny, but possibly to her inability to reconcile with her new reality'.
She went on: "The sign-off is less about the actual device and more about what it represents: a sense of belonging to a professional class and a world where she was respected and successful.
"It is an attempt to project an image of stability and normalcy in contrast to her current life.
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"Signing off her emails with 'Sent from my iPhone' despite not owning one may serve as a symbolic link to her former status."
Dannielle added that the strange signature could also be a means of 'Martha' subconsciously attempting to preserve her 'previous identity'.
"This small but deliberate act of deception may reflect her deep-seated need to preserve her previous identity, which has been shattered by her imprisonment," she adds.
"This insistence on a fictional narrative showcases the psychological complexities of coping with downfall. It also demonstrates how individuals might go to great lengths to retain some semblance of their former selves in the face of drastic life changes."
Baby Reindeer fact vs fiction
While Baby Reindeer is based on a true story, many viewers have been left questioning which parts were fabricated for the Netflix show.
We've separated the facts from the fiction.
How Donny and Martha met
In Baby Reindeer, Gadd's character Donny offers Martha a free drink after feeling sorry for her when she said she couldn't afford one.
This is true as Gadd's seemingly harmless act of kindness quickly snowballed into a shocking turn of events.
The amount of emails
Gadd's stalker sent him 41,071 emails, 350 hours of voicemail, 744 tweets, 46 Facebook messages and 106 pages of letters over four-and-a-half years.
In real life, she also sent him a variety of strange gifts, including a reindeer toy, sleeping pills, a woolly hat and boxers.
When the police intervened
In the series, Donny wasn't taken seriously when he initially reported Martha to the police.
According to Gadd, it was six years before they finally intervened.
Which details were fiction?
Gadd has spoken about how some details of the show have been changed to protect identities of those involved.
He explained that 'Martha' had been disguised to such an extent that he doesn't think she'd 'recognise herself'.
It's also unclear whether the real-life Martha went to prison.
In Baby Reindeer, she was sentenced to nine months in prison and given a five-year restraining order.
Though Gadd told The Times the stalking issue has been 'resolved', adding that he 'mixed feelings about it' because he 'didn't want to throw someone who was that level of mentally unwell in prison'.
Topics: Crime, True Crime, Netflix, TV And Film