HBO's stunning crime-drama 'True Detective' will come to an end on Sunday night (March 9, 2014) - at least for season one - leaving a complete void in the lives of all those who have followed Nic Pizzolatto's groundbreaking series over the past 7 episodes. Though we always knew 'True Detective' was going to be awesome, something different has happened with this series, expertly directed by Cary Fukunaga. Never before has Reddit seen such fervent post-episode activity, speculating on everyone little detail of the world Pizzolatto has created.

True Detective Woody Harrelson [L] and Matthew Mcconaughey [R] in 'True Detectives'

Should you be reading this, you'll know that True Detective follows two Louisiana State Police homicide detectives on the hunt for a serial killer responsible for a string of ritualistic murders. It's a sweeping, sprawling series set over three time periods across seventeen years and featuring endless philosophical and literary references that have left viewers dreaming up their own who-dunnit theories.

HBO's synopsis for the final episode, 'Form and Void', comes with the following information: "An overlooked detail provides Hart and Cohle with an important new lead in their 17-year-old case," prompting curious Redditers to speculate on that very detail. 

So - how will 'True Detective' end? Here's the most popular theories:

Marty is the Killer.

Though Harrelson's Marty Hart being the killer was a popular theory following earlier episodes, it's since become one of the most farfetched outcomes. Sure, Marty going crazy and shooting Reggie Ledoux seemed a little out of place and got us all suspicious, but Pizzolatto has consistently assured us that he's not trying to trick anyone with the True Detective finale. To out Marty as the killer would pretty much ruin all the good work done in the previous seven episodes. We're guessing the HBO billboard was a red herring, too. 

The Five Horsemen.

The most likely theory is that the Five Horseman, who have been consistently referred to throughout 'True Detective', are responsible for the ritualistic killings. We first saw the five masked men (or woman) on horseback surrounding Dora Lange in a photograph at her mother's house.

Then there was the gang rape scenario with Audrey and Maisie's dolls, and the five Lone Star beer can men that Cohle made while being interrogated by Papania and Gilbrough. Add to that the five masked figures in the snuff video that spooked Marty and we've got ourselves the culprits.

It's transpired that the Five Horseman are probably all members of the Tuttle family, with Billy Lee Tuttle, Sam Tuttle and Eddie Tuttle the obvious starting points. That leaves two more masked horseman, which could well be Sherriff Ted Childress (the cop who covered up the Marie Fontinot killing) and potentially the 'Lawnmower man' Errol who appears to fit into the family tree as Ted's son. 

We also know that the Five Horseman had three younger men responsible for capturing and drugging the victims. Reggie Ledoux and his brother (who housed the girls at their den) are almost certainly two of the three. See: Charlie Lange's conversation with Rust & Cohle regarding Carcosa. 

True Detectives season 1Cohle and Hart on the case in 'True Detective' season one

Audrey Hart

From the finale preview, it seems likely that Hart and Cohle manage to track down Carcosa - the "place down south" where women and children are "sacrificed." Hart's foreboding goodbye to ex-wife Maggie in episode 7 implies that things are going to get heavy and the preview hints at violence and potentially torture. 

However, the chat between Maggie and Martin was interesting for another reason: the discussion about their daughter Audrey, who has been linked to the cult/killing/Yellow King since the very start. We know she drew strange sexually suggestive pictures at school. We know she had sex with two boys at once. We know she formed her Barbie and Ken dolls into what appeared to be a rape scene. In the scene in episode 7, Maggie told Marty that Audrey had been selling artwork and had a boyfriend. It seemed as though Audrey was elsewhere, i.e, no longer living in the family home.

When the Daily Beast's Andrew Romano interviewed actress Michelle Monaghan - who plays Maggie - about her family's involvement after episode 6, she replied: "You mean my family, as in, my mother and father and that sort of thing? Yes, yes. Our family - everybody - is still going to be part of the plot going forward."

We're guessing that once Rust and Marty arrive in Carcosa, Audrey becomes a bigger part of the plot. And what about grandfather? He's the rich guy that complained about "everything" becoming sexualized in an early episode. Marty gave him short shrift on that occasion - but did he miss a vital part of the puzzle? 

Check out our piece on who could take over from McConaughey and Harrelson in 'True Detective season 2'.