Audrey decides to take back Lewis (Nigel Havers) this week, convinced that his scamming days are now behind him.
Well aware that her daughter Gail (Helen Worth) will be furious over the news, Audrey tries to conceal the rekindled relationship. However, it doesn't take long before the truth comes out.
Nicholls told itv.com: "The secret affair is quite exciting. Nobody should know about it, because they're giving Lewis such stick.
"It's rather difficult, really, as Weatherfield is quite a small community. There aren't many roads, so trying to keep away from the family is quite a difficult process. But they do have quite a lot of fun to begin with."
She added: "When the secret does eventually come out, it really is splat at the Platts', I can tell you! There's a lot of harsh words from both sides."
Lewis returned to the cobbles last month, claiming to be a changed man.
> Coronation Street Sue Nicholls fears Audrey, Lewis heartbreak
> Read more Coronation Street spoilers and news
Watch a preview of tonight's (March 12) Coronation Street double bill in the video below: