Mercedes has enjoyed an on-off fling with pub landlord Carl Costello this year, despite being engaged to his footballer son Riley (Rob Norbury).
Although Mercedes has recently tried to keep her distance from Carl, the storyline is revisited in next week's episodes as her sister Jacqui (Claire Cooper) finds out about the affair. Jacqui also learns that Mercedes is planning to fake a miscarriage after lying about being pregnant.
Jacqui is left disgusted by her sibling's behaviour and her discoveries leave Mercedes panic-stricken as she believes that her betrayal of Riley is about to be exposed to all.
Pictured: Mercedes and Jacqui argue over Riley.
However, pondering her character's next move, Metcalfe told Soaplife: "She wants Riley. She loves Riley. But she can't help fancying Carl. There's a difference between love and lust in Mercedes's eyes. Carl is really keen and if she gave him the nod, he'd be right back in there.
"If Jacqui keeps her mouth shut, Mercedes will be relieved she's still got Riley and won't be thinking about Carl - although I think they could end up in bed together again!"
Metcalfe also admitted that keeping Jacqui quiet will prove a difficult task as she seems determined to reveal the truth.
She said: "It's horrible. Mercedes feels like her world could collapse around her at any moment."
Hollyoaks screens the latest twists for Mercedes and Riley next week.
> Read more details of the storyline in our Hollyoaks spoiler section Get the Inside Soap magazine on your iPhone or iPad