The actor, 25, stars as evil killer Meena Jutla, whose reign of terror has caused havoc in gripping scenes in the ITV soap.
As Meena’s trial comes to an end she looks set to get her comeuppance for offing several characters.
But Sandhu has now revealed that there is more drama to come before the killer’s story reaches its conclusion.
Appearing on ITV’s Lorraine, she said: “I always imagined it would go a certain way, but it is so much better than that. It’s just so dramatic and there’s one thing that is going to come out tonight where I actually dropped my script (and gasped), ‘I can’t believe it’.”
She went on: “This is a big, big secret that I think the audience will love and will be really exciting and just adds another dimension to Meena, Meena’s relationship with her sister and the whole storyline.”
The actor told presenter Christine Lampard – who was filling in for the show’s usual host Lorraine Kelly – that it felt very “emotional” to be working on Meena’s finale.
She said that playing the baddie had been “a delight”.
“I feel like Emmerdale just went into my brain and saw my dream character, plucked her out and put her on a page,” she said.
“She’s just an absolute dream of a character.
“She gets to go crazy, wild and then you see moments like last night when she was on the stand, and she’s an incredible actress.”
“It’s just been a dream,” she added of playing the killer.
Lorraine airs on weekdays at 9am on ITV and ITV Hub.
Emmerdale is on ITV at 7.30pm.
Watch: Emmerdale Soap Scoop! Meena prepares for her trial