After more than 50 years, it was a trio of amateur sleuths who cracked the Zodiac Killer's cipher - and if that doesn’t make you want to flick on an episode of Unsolved Mysteries and whip out your notepad then I don’t know what will.
The infamous serial killer - who has still never been caught - terrorised northern California in the 1960s with five confirmed victims, but said they'd killed 37.
To taunt police, someone claiming to be the killer sent in coded messages to law enforcement and the media through the late 80s, before going silent in the 1970s.
One such message was the 340 cipher - given the name as it contained 340 characters - which left cops and codebreakers stumped for 51 years.
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Some experts even reckoned the code could never be broken, but they were prove wrong in 2020 by amateur codebreakers Dave Oranchak, Jarl Van Eycke and Sam Blake.
The three men, who didn’t even all live on the same continent, met on an online true-crime discussion board and started collaborating during the COVID-19 pandemic.
Despite having no background in cryptology – Oranchak is a computer programmer in the US, Blake a mathematician from Australia, and Jarl Van Eykcke a warehouse operator in Belgium – the three men worked together to finally find a solution.
The trio spent hours trying to crack the code, using special software that could work through thousands of potential solutions, and finally, in November 2020, they did it.
Uncoded, the cipher, which contains no punctuation, reads: "I hope you are having lots of fun in trying to catch me.
"That wasn't me on the TV show which brings up a point about me
"I am not afraid of the gas chamber because it will send me to paradice [sic] all the sooner.
"Because I now have enough slaves to work for me where everyone else has nothing when they reach paradice so they are afraid of death.
“I am not afraid because I know that my new life will be an easy one in paradice death."
Their solution was recognised by the FBI, which shared a statement that read: "The FBI is aware that a cipher attributed to the Zodiac Killer was recently solved by private citizens.
"The Zodiac Killer case remains an ongoing investigation for the FBI San Francisco division and our local law enforcement partners.
"The Zodiac Killer terrorised multiple communities across Northern California and even though decades have gone by, we continue to seek justice for the victims of these brutal crimes.
"Due to the ongoing nature of the investigation, and out of respect for the victims and their families, we will not be providing further comment at this time."
However, as the FBI points out, while the cipher may have been solved, the identity of the killer - or killers - has never been revealed and the case remains open.