Lacey shared a moment with Ally (Dan O'Connor) earlier this month and is now keen for things to develop further, even though the mysterious Australian is her sister Ash's boyfriend.
Keen to impress Ally, Lacey starts dressing more provocatively around the Kane house before finally attempting to kiss him - but will she get the reaction she is hoping for?
Digital Spy recently caught up with Georgia Bourke, who plays Lacey, to hear about the shock storyline and more.
What has this storyline been like to film?
"I didn't really see it coming so it was a bit of a shock, but it has been quite fun to film. It's something different, so I think it makes a nice change for the character of Lacey."
Why is Lacey tempted to betray her own sister by pursuing Ally?
"I think part of the reason for that is Lacey and Ash have a bit of a strange relationship anyway. Lacey went out of the family home for quite a few years while she was away at boarding school, so I don't think they've become as close as you would expect.
"Also, Lacey is not a very good judge of character when it comes to boys. As soon as she thinks Ally is showing her a bit of attention, she's keen to jump onto that regardless of the consequences."
Does Lacey feel any guilt about what she's doing?
"I think there are probably a few moments when Lacey realises that it's wrong, but she also thinks that Ally is spurring her on. She's encouraged by that and she's not thinking too much about the fact that it's her sister's boyfriend. To Lacey, he's just this man who's living in her house and giving her attention. She's quite flattered by that."
Has Lacey always liked Ally?
"I wouldn't say she's liked him from day one. When Ally first moved in, her attention was focused on Dylan at college. But when Lacey and Ally were playing Aussie Rules in the park and fell to the ground, there was a moment between them. Since that point, Lacey has always thought that there is something between them, and it's built from there.
"Now Lacey wants things to go further, so at the beginning she plays it cool and it builds over time. Once she thinks that she's getting something back from Ally, she'll step it up a notch."
How does Ally react when Lacey walks around the house in just a towel to impress him?
"Ally is a bit shocked! He obviously sees her as the little girl of the house because she's the youngest in the family, so I think that shocks him. But on the flip side, I think Ally is flattered because he's now got attention from both of the Kane sisters. He's not going to tell her to stop anytime soon."
Lacey also invites Neil around and provokes a row by hinting that he's being too forward…
"She does, and again, that's another example of her trying to get Ally to show his affection towards her. Lacey is not really that bothered that Neil is being left in the firing line because of that - she's just using him to get the reaction she wants from Ally."
How does Lacey and Ally's kissing scene come about?
"The kiss happens directly after Ally has pinned Neil up against the wall to warn him off. From that, Lacey has decided that Ally does fancy her - she's definitely got the reaction that she wanted.
"Lacey thinks that's the perfect opportunity to kiss him, so it'll be interesting to see how Ally reacts to that because I don't think he's expecting it!"
Do Ash and Callum pick up on any of the goings-on between Lacey and Ally?
"They don't, because up until the kiss it's all been quite subtle. It's just been the odd look or glance - nothing too obvious. Lacey is also quite careful with what she's doing. Although she doesn't care too much about Ash and her feelings, she knows that it shouldn't be happening, so she'll only pursue Ally when nobody else is around."
How do you think Ash would react if she found out?
"I don't think she'd be too happy! I think she'd be shocked at both Ally and Lacey. Her pride is important to her, so she'd probably just go berserk, I imagine!"
Does Lacey see the kiss as the start of something?
"I think she's certainly hoping that something more could develop. Lacey is under the impression that Ally fancies her, so she's really keen to move things forward. She hopes that kissing Ally will perhaps be the start of a relationship."
Were you nervous about filming the kissing scene with Dan?
"It's just part of the job, really. Dan is lovely and we get on well, so it's fine. It wasn't too painful! By that point, we'd done a whole day of filming, so it was just part of the scenes that we were doing and I wasn't too nervous coming towards it. It's always a little bit awkward filming kissing scenes, but it wasn't too bad."
How much of a mistake are the Kanes making by trusting Ally?
"From watching the programme I think they're making a big, big mistake! He's a very, very dodgy character and I think it's clear to the audience that whatever he says is not quite the truth.
"The Kanes don't even know who he is or where he's come from, but they've allowed him into their house and trusted him completely. I think that's probably a massive, massive mistake."
We've waited a long time to find out more about Ally and what he's up to. Are answers coming?
"Yeah, I'd definitely say that explanations are on the way. By Lacey and Ally having this interaction, it's going to maybe bring up more drama and there'll be more developments coming up. You're definitely on the way to finding out who Ally is and what he's about…"
Now that Martha is back on the scene, can the Kane kids ever forgive her?
"You can never say never, but I think especially with Ally around, that's going to be a long, long battle. Martha is very determined, but on the flip side, the kids are very stubborn. They all think they know best so a resolution is never going to be easy, but maybe it will happen over time."
Is there any hope for Lacey and Dylan?
"I think there's some hope for them and it's a shame how things have turned out, because Dylan has been lovely. Really Dylan is what Lacey is looking for - someone who is showing her some attention. For now, Lacey's sights are set on Ally and for the immediate future, that's where her attentions are going to lie, but who knows?"
Do you enjoy working with Mikey, who plays the role of Dylan?
"Yeah, I've really enjoyed working with Mikey. I was in his audition right at the beginning, so I've known him for quite a while now. It's nice to see him come out of his shell, and he's really getting on well at Hollyoaks - he's doing a great job. It's been really nice to see that and he's a really sweet guy."
Do Lacey and Phoebe have more scenes on the way?
"Yes, there are a few more scenes on the way, which I'm quite looking forward to. I really like their friendship and I think they work well together. It's not your typical friendship, and there'll definitely be more depth between them as they learn a bit more about each other."
Could Lacey become a friend to Esther as her bullying ordeal worsens?
"I hope so, because there's been moments in the past which show that Lacey is on Esther's side. The thing with Lacey is that she is quite selfish and self-absorbed, so at the moment, her attention is focused on Ally and she's not completely aware of what's going on with the other sixth formers.
"If something was immediately put in front of her - a situation where Esther was being bullied - I think she would stick up for what's right. I hope they can be friends because Lacey needs more friends, and Esther definitely does! It might or might not happen, we'll have to wait and see."
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Hollyoaks airs weeknights at 6.30pm on Channel 4, with first look screenings at 7pm on E4.