Jean Slater (Gillian Wright) will leave Albert Square without warning on Thursday night’s episode of EastEnders after her relative exposes her secret.
For weeks the Slater matriarch has been hiding the fact she might have cancer from her family and friends.
But the shocking news was finally revealed after Kat Moon (Jessie Wallace) stumbled across one of her letters from the hospital.
When Alfie Moon’s wife confronted Jean on Tuesday’s instalment of the BBC soap, Jean begged her not to tell her daughter she might have the disease.
Stubborn as always, Kat will defy Jean’s wishes and tell Stacey Fowler (Lacey Turner) the truth about her mother’s cancer diagnosis later this week.
Furious the information was not given to her by her mum, Stacey will march over to Jean to find out what is going on.
Concerned about her health, Stacey urges Jean to go for the tests immediately to confirm whether she has cancer.
But Jean will be having none of it when Stacey insists she goes to the appointment straight away to get some clarity.
When Jean later overhears Kate and Stacey talking about her she panics and packs a bag to leave.
With her belongings in tow, the mother-of-two heads to the tube station – but will she leave Walford for good?
EastEnders fans were stunned when Kat discovered Jean’s secret, with many rushing to Twitter to discuss the moment.
One person wrote: “Kate knows Jean’s secret,” while another added: “OMG Kat found out about Jean!”(sic)
A third contributor said: “Them scenes between Kat and Jean were so emotional.”
Someone else shared: “Jean this is Kat your talking to she’s the biggest blabbermouth going no way will she keep it hidden.”
Jean’s son Sean (Robert Kazinsky) is set to return to the East End later the year to support his beloved mother.
Although his stint is likely to be brief, EastEnders producer Kate Oates previously teased the possibility of Robert sticking around for a much longer plot.
Speaking to Express.co.uk about whether Sean’s storyline could end up going beyond Jean’s current health problems, Kate said: “Depends if I can tether him to the table!”
“I’ve really, really enjoyed working with him,” she continued. “He had such a massive input in his comeback story and he was in LA and we were FaceTiming and talking about the stories, and he gave us so many amazing ideas.”
She added: “He is brilliant, I am so excited to see it come to life on screen because he is exceptional.”
EastEnders continues Thursday on BBC One at 7.39pm.