Forget the ‘Who killed Lucy Beale?’ mystery; that’s done, dusted, and we all know that Bobby (aka ‘that shifty little mug’) was the one who bumped her off.
But, while that question has been answered, EastEnders bosses have given armchair detectives an even bigger mystery to solve.
Yup, we’re talking about Stacey Branning’s key.
The long-running storyline kicked off last year, when Stacey returned to Albert Square with a key around her neck that she was determined to keep safe.
As we all know, the little girl - Zoe - was raised by Kat’s parents, who told the rest of the family that she was their own biological daughter.
Hence the iconic “YOU AIN’T MY MUVVA” scene.
But, as Kat’s parents wanted to keep her little girl in the family, wouldn’t they have done the same with her little boy?
And, you know, wouldn’t it have made sense for them to give him to, say, Jean Slater?
After all, we know that Sean was the one who gave Stacey the key in the first place.
And we know that Jean Slater, upon seeing the key around Stacey’s neck, completely freaked out and violently grabbing it back.
Is Sean actually Kat's son? Could the key have something to do with Sean's parentage? Could it open up a safety deposit box containing his original birth certificate?
Soapstar Lacey Turner, opening up about her alter-ego’s key, told Digital Spy: "God, the key. I wish I knew!
“It does come up again but I still don't know what it's for. I can't even tell you.
“I’ve racked my brain about it and none of it really makes sense."
Teasing the upcoming ‘fright-night’ Halloween episode, in which her character is hospitalised following an electric shock, Lacey added that it will have repercussions for her relationship with Martin.
"She's very much into Martin and her little family but I'm sure it'll never stay that way. It never does. Just as you get used to someone there's someone else! Martin's her safe option but she's not one for having just one, is she?"
She added: “I want her to be with Martin. He's safe and he's funny and I think he'll make her happy."