In recent weeks, fans have seen Katie continue to date Henshall (Michael McKell), unaware that he was responsible for the blaze which claimed the lives of Terry and Viv.
However, speaking to All About Soap, Winward confirmed that Katie finally sees Henshall's true colours after agreeing to go away for a short holiday with him.
The actress explained: "She thinks leaving the village for a few days will do them both good - especially if it means being away from Andy. But then she stops off at his house on her way home and is stunned to find press clippings about Henshall's first wife, who died in an arson attack."
She continued: "The pieces all start to fall into place for her and she finally realises that Henshall was behind the fire. She still doesn't quite know how he fits into the bigger picture but she knows there's something he's been hiding.
"Anything could happen - Katie is terrified at this point. She knows that Henshall isn't the trustworthy man she thought he was and so he is bound to be very angry if he knew what she'd discovered. Things are about to get very exciting - watch this space."
Earlier this week, Winward revealed that she had recently filmed her "most intense" Emmerdale scenes to date.