Lauren Branning (Jacqueline Jossa) has been left paranoid following the murder of her best friend Lucy Beale - and with good reason, given that she has become victimised by a terrifying stalker.
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In last week's Halloween episode, Lauren finally chased down and confronted her shadowy follower - wearing a suitably creepy Weeping Angel mask - only to discover it was her sister, Abi (Lorna Fitzgerald).
And now EastEnders producer Dominic Treadwell-Collins revealed that Abi has only just begun to show her true colours, tweeting: "#BadAbi still hasn't finished terrorising her sister... @LornaFitz0 @jacquelineMjos #EastEnders tonight 2000 hrs"
Meanwhile Lorna Fitzgerald has explained her character's motives in a recent interview with Digital Spy.
She explained: “Abi’s annoyed at Lauren always getting so much attention. She just wanted to scare Lauren.
“Abi has just reached the end of her tether – She just wants somebody to notice her!”
This storyline is set to mark a real change in Abi, who even ends up attacking Lauren next week as her aggressive side really gets to come out - but could this mean that she might have been the person who killed Lucy?
Lorna certainly hopes so!
She explained: “I honestly don’t know who it is… but I would like it to be Abi because it would be a challenge for me to act it.”
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A lot of armchair detectives have already suggested that Abi COULD be Lucy's murderer - especially after she recently killed the Branning's loyal dog, Tramp, and simply responded with a deadpan: "things die".
Throw in the fact that she was furious her dad Max (Jake Wood) was sleeping with Lucy and you have a recipe for disaster - butcould little Abi REALLY be a murderer?
Let us know via the comments box below now...