Kate had previously teased Jean (played by Gillian Wright) would be facing a challenge in 2019, and now she has revealed the nature of the trial.
As EastEnders viewers know, Jean has bipolar disorder which has been at the centre of some storylines in the past.
But this year fans of the BBC soap will see how her mental health issues impact her in a different way.
Kate spilled all about the New Year plot in a Q&A video posted to EastEnders’ official Twitter page.
She said: “We’ve got a big story coming up for Jean.
“She’s going to have a challenge coming her way where we look at her mental health through the lens of her physical health. So I’m excited about that one too.”
However, it doesn’t look like it will be an entirely negative experience for the much-loved Slater.
Kate had previous told Express.co.uk: "Jean’s going to have a bit of a new challenge coming her way that she might find it’s the best thing that’s ever happened to her.
“So there’s some fun stuff to challenge her there, along with Lacey