Ever since her death on Good Friday 2014, EastEnders fans have been desperately puzzling over who killed Lucy Beale.
With so many suspects, red herrings and plot twists, we've fingered everyone from Abi Branning to Les Coker as the murderer - and none of us feel any wiser as to who did the dark deed.
But now one dedicated armchair detective believes he has solved the mystery.
And it was all through re-watching There's A Killer Amongst Them, the original advert put out by BBC One.
Did you spot the killer?
No?
Well, Andy Fraser - writing on his website at UFK.hubpages.com - has broken it down for us.
He writes: "So, the clip shows a panoramic shot of the hallowed Square de la Walford for a miniscule 3 seconds and then it proceeds to trot out the 'red herrings' which is fine and dandy.
"[But] Skip back to the opening shot, the 3 seconds of lead-in. That's where the REAL clues are."
He continues: "See the four people?
"There are the two in the Gardens. One's a blonde, that's for sure, and the other is a guy holding his arms out to the blonde.
"Those are characters A & B.
"In the foreground we see character C, watching A & B from where the Butcher's house would be. Character D can be seen walking away beside the rear of a car outside the Beale's house."
While Andy refused to reveal his thoughts about who the characters are in a public online post (he is reportedly in "enough trouble as it is" over his EastEnders speculation), he does insist that identifying these four people will tell us:
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WHO BURIED THE PHONE AND PURSE
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WHY THEY BURIED IT And FOR WHOM THEY WERE COVERING FOR
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WHO THE KILLER IS
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WHY LUCY WAS KILLED
Many have speculated that it is Lucy and Lee Carter standing inside the gardens together, especially after it was revealed that the words 'Lee, stop it' were scrawled in a crossword completed by Lucy Beale's ghost.
However others have suggested that the two inside the garden are, in fact, Jay and Lola, and that they are being watched by Ben Mitchell as Max Branning loads up his car nearby.
Could this mean that Ben and Jay, who buried Lucy's belongings in the allotments, have a LOT more to do with their death than they say they did?
Or does it mean that they are all covering up a crime for none other than… Abi Branning?
Yup, little Abi has been a hot favourite to be the killer ever since we watched her lose her temper and try to drown her sister Lauren.
Plus there's the fact that she was seriously NOT happy her dad had been having an affair with Lucy, that she uttered a cold 'things die' when she ran over and killed her beloved dog (creepy), and that she doesn't want anyone to find out what she did on Good Friday.
Throw in Emma hurling a deathbed accusation at Max ("She wasn't there [and] you know") after confronting the killer, and you have a recipe for success.
So: Abi killed Lucy in a fit of rage, her dad was the one who moved the body to Walford Common for her (making him Character D), Ben Mitchell could have seen the crime (Character C), and Jay knows about it and has confided in Lola (A & B).
It kind of makes sense, doesn't it?
Then again, this could all be just another red herring.
What do you think of the clues laid out in this trailer? Let us know via the comments box below now.