Charlie Slater and Mo Harris return to the Square next week to see Stacey’s newborn baby Arthur and drama soon follows.
Kat is delighted to see her dad again, but with his death looming, how much more can the Slaters take?
Meanwhile, Stacey is struggling with motherhood as she battles a rare mental illness.
Stacey is set to suffer from postpartum psychosis, which causes mood swings and hallucinations.
Concerned about Stacey, Kat tries to get to the bottom of what’s wrong.
Dot grows concerned for Stacey, too, when she finds her and Arthur in her house – but what is Stacey about to do?
Elsewhere, Alfie receives a call from his doctor…
Before he left the Square, Alfie was told the upsetting news that he had a brain tumour.
Determined to make Kat happy, he refused treatment and the couple moved to Spain.
Later, Kat receives life-changing news as Sister Ruth, played by acting veteran June Whitfield, returns to EastEnders with a huge revelation for Kat.
As viewers will know, Kat is currently unaware that her daughter Zoe was a twin.
Sister Ruth, still feeling guilty about the secret, arrives in Albert Square to tell Kat the truth.
Understandably shocked, what will Kat do?!
EastEnders airs these scenes on Monday the 4th January 2016 at 8pm, Tuesday the 5th January 2016 at 7.30pm, Thursday the 7th January 2016 on BBC One and BBC One HD.