One case that caused quite the stir was that of Rey Rivera, a businessman who was found dead in 2006.
The episode titled Mystery on the Rooftop looks at the strange occurrences surrounding his disappearance and the discovery of his body at the Belvedere Hotel in Baltimore, where he had seemingly fallen from the top of the building and crashed through the roof.
There's plenty of suspicion around his death, considering the sheer amount of theories about how he got in and around the Belvedere Hotel anyway, let alone the unusual circumstances around his disappearance which came after he received a mystery phone call.
The Unsolved Mysteries team are hoping to find answers for Rey's wife, Allison, and the rest of his family, but the case has gone cold. But there's plenty of fresh evidence that's emerged during the investigation, from a strange occurrence before Rey disappeared, to the unusual appearance of a token penny on the body after death.
So what exactly happened to Rey? What was in the note he left behind? And who exactly is Porter Stansberry?
Here's all the theories behind the unsolved case, and some of the unanswered questions.
Theory one: "Rivera's death was linked to David Fincher's The Game"
Ever since the episode aired on Netflix, amateur detectives have been inspired everywhere, with fans looking into clues and coming up with theories of their own.
One of the latest theories links Rivera's death to David Fincher's film, The Game, which features a character dying in a similar way to Rivera.
The theory, posted on Reddit last week, points out a connection between a note left behind by Rivera and the great fall which initially appeared to cause his demise (although the forensic team determined his cause of death as “unexplained”).
The internet detective noticed The Game was listed in Rivera’s note, which referenced the Freemasons and family friends as well as films, TV shows and books that he enjoyed.
The 1997 film follows a man who participates in a scheme which blurs his concept of reality and ends with him jumping from the roof of a building through a glass ceiling – and the theory suggests that Rivera was copying the events of the film.
The theory has gained so much attention that the show's co-creator Terry Dunn Meurer has even spoken out about it, however, Rey's wife Allison doesn't see any significance in it.
Speaking to EW, Meurer said: "I spoke to Allison Rivera about that – she’s spent a lot of time with that note, as did the FBI, just going through the note trying to figure out if there were any clues or anything else in there. She doesn’t place any significance on the movie The Game."
Theory two: "Rivera was dropped from a helicopter"
A newly-released clip which didn’t make it into the series presents a more speculative theory, that Rey may have been dropped from a helicopter.
“I know it sounds crazy, but this is the kind of case that makes you look at more strange theories,” investigative journalist Stephen Janis explained in the new video.
“You’ve got no real evidence. Given the hole and given that nobody saw him enter the building – he had to come from somewhere else.”
Gary Shivers, who previously worked at the Belvedere (the hotel where Rivera was found), agreed with this theory, saying: “That’s the only possible thing I can think of.”
The new clip has caused some confusion, due to the fact that no witness has admitted to hearing or seeing a helicopter at the time, however, police detective Michael Baier offered an explanation to this.
Delving into the theory, he said. “Airspace issues? People hearing the helicopter? You’re not going to hover down in a helicopter that low. If he would have been dropped at an altitude higher than the building, who knows where he could have went.”
Theory three: "Rivera jumped to his death"
One of the leading theories, and the one Baltimore officials appeared to lean towards, is that Rivera died by suicide.
Having plunged through the roof of the room where he was found, it was assumed Rivera had jumped to his death.
On the Unsolved Mysteries Reddit page, one user pointed to the "bizarre" note Rivera had left as evidence that he was someone with an undiagnosed mental illness.
It began with Freemason-related wording — "brothers and sisters, around the world right now volcanoes are erupting, what an awesome sight" — and also contained a long list of family members and celebrities who Rivera wanted to make "five years younger". The note had been folded up very small and taped to the back of his computer.
However, a number of factors led to his death being ruled as “unexplained” and many doubted whether he had in fact taken his own life.
In the episode, his loved ones insist that it would have been out of character and emphasised that he exhibited no signs of mental distress at the time of his death.
Rivera had just had a new lease on life — a lovely wedding to his wife Allison and a steady job with his friend Porter Stansberry.
There's also a possibility that the letter could have been written in code, if Rivera did indeed have ties to the Masons, which is why many are unable to make sense of it.
Theory four: "Things were staged"
In the first episode, reporters and detectives expressed doubt about Rivera falling through the roof. There were three potential jumping points at the hotel: the very top roof, the parking garage, and the 11th-floor ledge.
Many were sceptical about the first two, as it would've been either too high or too far for him to land through the meeting room roof.
The 11th-floor theory would only be possible if Rivera went through a room or office since none of the hallways led to the ledge. Even so, the room windows were very small and no one mentioned seeing him.
As well as this, the camera on the rooftop was also disconnected, adding more mystery to the case.
Some other pieces of evidence also didn't make sense, two of those being that Riveras phone and glasses were intact when he was found.
The forces that killed Rivera did severe damage to his body, so it struck people as odd that not a scratch could be found on those items, leading many to speculate that they were staged and that someone had positioned Rivera's body beneath the hole as well.
The medical examiner also told Rivera's wife that the way his shins were broken weren't consistent with a fall.
Theory five: "Rivera lost someone money"
Another major theory revolves around Rivera's work with Agora Inc, with whom Stansberry's company is affiliated with.
Rivera wrote the Rebound Report for a division of Agora, but according to WBAL-TV Baltimore, he was unhappy about his work because some of the stocks he wrote about weren't rebounding — which meant lost money for anyone who bought them based on his advice.
In the fall of 2005, Rivera left Agora full-time and began producing videos for the company under contract.
Because his filmmaking career wasn't paying the bills, Rivera and his wife moved from Southern California to Baltimore.
Here, he worked with his old high school water polo buddy, Porter Stansberry, who had his own financial newsletter business.
Rivera helped with Stansberry's business in several capacities as a writer and freelance videographer.
Before Rivera was hired, Stansberry's company was already under investigation. According to The Baltimore Sun, the business was ordered to pay $1.5 million in restitution and civil penalties for "disseminating false stock information and defrauding public investors through a financial newsletter." Stansberry denied any wrongdoing.
On the week of his disappearance, Rivera's home alarm went off two times. And on the night he went missing, Rivera picked up a call from work, but it was impossible to determine who had called him because the call came from a switchboard.
As the case unfolded, Stansberry was said to have obtained a gag order to prevent employees from legally talking about Rivera.
No one from Agora has ever been implicated in Rivera's death. According to Unsolved Mysteries, the company's staff was advised not to speak about the case with the media or law enforcement, and Stansberry has continually declined to be interviewed - though producer Terru Dunn Meurer has confirmed she did speak to hi.
Rivera's brother Angel suggested that someone powerful may have lost a lot of money after one of his publications got out.
What exactly was in Rivera’s note?
The different theories have led to viewers asking questions, one of those being the contents of the letter Rey left behind.
After his disappearance, Rey's wife went searching through his office space, and that's when she came across a small note behind the computer.
In the documentary, she says she knew the note had been written on the day he went missing as she found scraps of it in the bin.
According to 11 News, the note was addressed to brothers and sisters and referred to a well-played game.
It named people who had died, including actor Christopher Reeve and filmmaker Stanley Kubrick. It also contained a long list of people Rivera knew and was related to, with a request to make them and himself five years younger.
However his wife says there were significant names missing, which she found "weird".
The note introduced an element of the case that involved Rivera's apparent interest in the Freemasons, as it began and ended with phrases used in the Masonic order.
The FBI cleared the note as unusual but not suicide intent.
Was Rivera connected to the Freemasons?
Another question Rey's death has raised, is whether he was connected to the Freemasons, due to the "coded" element of his letter.
Confused by the contents of the letter, Rey's wife decided to put a sentence into Google and it came up with results related to the Freemasons.
Rivera's family and friends said his fascination with the Freemasons centred on their reputation as an organisation with secrets, and in the Netflix episode, Rivera's interest in the group is covered.
However, according to WBALTV, there were more details on Rivera's interest in the Freemasons.
In a report, the publication stated that Rivera had talked with a member of the Maryland lodge to inquire about joining.
And on the weekend before his disappearance, he spent time reading the book The Builders, a study of masonry.
They add that on the day of Rivera’s disappearance, he went to a bookstore and bought the book Freemasons for Dummies.
Who is Porter Stansberry? And where is he now?
Born in 1970, Stansberry was Rivera's childhood friend and is known as an author and financial publisher.
After they’d both established different paths later in life, The Cinemaholic notes that Stansberry didn’t want to part with his friendship with Rivera. He persuaded Rivera to move to Baltimore with his wife to join his company.
Stansberry - who is now in his 50s - continues to live in Baltimore, Maryland as the founder of Stansberry Research.
He is also an editor of the online magazine American Consequences, which launched in 2017.
Viewers of Unsolved Mystery have become interested in whether he's spoken out about Rivera's death.
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At the beginning of the episode, Rivera's wife Alison mentioned that he offered a £1000 reward for anyone who might have seen Rivera during the days of his disappearance.
However, the show suggests that he hasn't made any further comments and he maintains his privacy.