A cold case detective starts researching a serial killer, and begins linking him to some of the most high-profile murder cases in American history.
The killer's moves and motives line up suspiciously well with these murders, and so the detective keeps digging, writing him a letter asking for a confession. The killer soon writes back ...
This sounds like the teaser for a terrible B-movie - or a terrific one - but this is the true, twisted tale of Edward Wayne Edwards, who, according to former FBI cold case taskforce detective John Cameron, may be one of the most prolific killers of all time.
Edwards was officially convicted of five murders during his lifetime, but Cameron believes he killed hundreds of times, setting up others for the murders along the way. The pair traded letters over a nine-month period, until Edwards died in 2011, aged 77.
Cameron claims Edwards was responsible for some of the most heinous murder cases over the past half-century, including the West Memphis Three murders, the Zodiac killings, the Teresa Halbach murder - as recently featured in the Netflix documentary Making A Murderer - and even the slaying of JonBenet Ramsey.
It all sounds rather fanciful, until you look at the evidence and realise that Cameron's theory makes a lot of sense.
He first became interested in Edwards in 2010 after reading his 1972 autobiography The Metamorphosis of a Criminal: The True Life Story of Ed Edwards - ironically about how the former criminal had reformed - and realised more than a few dates and facts lined up with unsolved murders.
"I pulled his records, because I worked in Deer Lodge Prison for the parole board," Cameron told news.com.au.
"I placed Ed in Great Falls, through his records, on the day we had a couple on a Lover's Lane executed. I confronted him by letter asking him to confess. It turned into a writing game for nine months [until Edwards' death], him leading me to open my eyes and look at the big picture. The Zodiac was just a small part of what he had done."
Cameron soon began linking Edwards to other crimes, his movements mirroring a string of murder locations over the decades.
"The Zodiac Killer teased the world with his identity in puzzles and letters", Cameron explains.
"Within the first two months of the investigation I knew he was the Zodiac Killer because we solved his identity cipher [a coded message sent to San Francisco media by the killer] and he responded by letter [claiming] to know the Zodiac Killer. The Zodiac Killer wanted to be the most evil criminal mastermind. That's why he sent the puzzles, teasing us with his intelligence."
Edwards was drawn to the media's obsession with murder cases, and used this to his advantage; oftentimes the "victim" in Edwards' killings was the person he set up for the murder, rather than the person he killed, according to Cameron.
"He kept telling me that we didn't know the entire story", he continues. "The Zodiac set people up his entire life. That was the point Ed tried to make with me before he died. He set people up."
Cameron explains that Edwards was a ritual killer, with his murders occurring on dates that tie to the occult, Catholic holidays, US holidays, and important dates in his life, such as his mother's birthday and the day of her death.
Teresa Halbach - the subject of Netflix documentary Making Of A Murderer - was murdered on Halloween, a date that looms large in Edwards' legacy. He was living an hour from the murder scene at the time, and had previously killed in Wisconsin - a fact that may have gone undiscovered if it wasn't for his daughter making a gruesome discovery and tipping off police.
"She watched a special on a 1980 Wisconsin double-murder and remembered her dad taking her and her brothers to the scene", Cameron recalls.
"This murder ended up being his undoing and it occurred 65km from Avery's Auto Salvage [where Halbach's body was found].
Ed wrote about Wisconsin in his book and that was a clue that he had killed there. He killed people whose names were contained in his book. He killed in states he named in his book. The name Teresa is a big name in his book, and Wisconsin, so he would have spent two years preparing to kill Teresa Halbach in Wisconsin."
Cameron also posits the name "Avery" was another link. "Steven Avery became the fall guy because of his name", he claims.
"Paul Avery was the San Francisco Chronicle reporter who chased the Zodiac his entire career. Ed sent him what is known as the Halloween Card, which told Avery that there was a clue to his identity." The card contained the numbers 6-14-33: Edwards' date of birth.
Another chilling coincidence is that Edwards seemingly appears in the background of the Making Of A Murderer documentary.
"He was known to appear at the scene of the crimes", says Cameron. "'I'm Always Watching' was his motto. He was always in front of everyone and nobody saw it."
While the man in the background of a shot looks startlingly like Edwards, Cameron hasn't been able to confirm this is the same man.
However, what is certain is that Edwards appears in yet another crime documentary: HBO's Paradise Lost, about the murder of three young kids in West Memphis, which was pinned on three anti-social teenagers despite scant evidence. Edwards stands at the murdered boy's gravesite, holding a cane and a one-dollar bill in what Cameron believes is more coded gloating.
"Who knows what ruse he used, but he conned a guy named Doug Cooper who was in charge of filming [into being involved]. On the same day that scene was filmed, someone tried to frame Mark Byers, the victim's father, by introducing a knife of Mark's to Doug Cooper.
"HBO had a big investigation after that was filmed because there were suspicions that someone had groomed their way into the investigation. If you watch the clip you will see what Ed is doing. He is holding the cane that was used to beat the boys, he's flashing the one dollar bill with the Egyptian Pyramid and Osiris' all seeing eye [similar occult imagery was a key theme used by prosecutors during the trial], and he places the money in his wallet."
It's a stretch, sure, but why on earth would Edwards be there at all if not to gloat? Cameron says it's all part of his obsession with being public, yet one step ahead of prosecutors. So, assuming Edwards was the prolific killer Cameron believes him to be, how was he able to evade detection for all these years?
"He was brilliant, had no conscience and was always inside the cops under assumed identity", Cameron explains.
"When he got identified in 2010 as a serial killer, cops all over the US recognised him. He had been an informant since 1950. That is why everyone has such a hard time with Ed. He fooled us all, and that is what the Zodiac Killer said he was doing. He laid all the pieces of the puzzle out to be solved by someone smarter then him."
Which may be the crux of how he was able to avoid detection for so long - nobody likes being made a fool of.
"There is a lot of egg on high-powered faces", he notes, "and that is why everyone is trying to discredit Ed."
Cameron believes he knows the truth. "The letters and puzzles were always the answer."