Befriending Seth as they both attend an outdoor activities retreat in Wales for the celebrations, bad boy Warren arranges for the teenager to lose his virginity by sleeping with a stripper.
However, with Seth on drugs, he later wakes up with no recollection of what he's been up to. The only clues are blood-stained sheets and evidence of a butchered body…
Has Seth lost control and killed the stripper while under the influence, or is there another explanation? Only time will tell, but Digital Spy recently had a chat with Miles Higson - who plays Seth - to hear more about the dark storyline.
This is the second year running that you've featured in Hollyoaks Later, so were you pleased to be chosen for it again?
"Yeah, definitely! It's always quite a change from the normal Hollyoaks so you get to do something different, and it's like being in a film. It's great to be involved in this - it's more fun and it's really nice to have your own storyline and show what you can do."
How did it compare to working on last year's series?
"It was completely different, because this year we had a completely different storyline and were working with some different people too, so it seemed like a different experience altogether doing it the second time round."
Seth is attending Riley's stag weekend, but how difficult is it for him to carry on keeping the secret of Mercedes and Carl's infidelity?
"It's very difficult for him, and events which take place in the late-night episodes make it even harder for him to keep this secret, because he's got so much else going on. You're going to see a really difficult time for Seth, but hopefully he'll pull through it."
"Yeah, and that was interesting - to work with him and get to know him a bit better. I really enjoyed filming the scenes with Jamie - it made a really nice change, because it was a completely different character dynamic to anything that Seth's experienced before. That was enjoyable."
Were you nervous about filming the scenes with the stripper?
"Yes, it was extremely nerve-wracking! (Laughs) It was one of the maddest things that I've had to do on Hollyoaks, so it'll be fun to see it going out on air. I've seen bits of the episodes already, but the bits with the stripper I'm dreading! But I'm sure it'll be alright."
How does Seth react when he wakes up following his encounter with the stripper and finds blood everywhere?
"It's utter confusion for Seth. He's been on drugs due to some peer pressure, and he's got absolutely no recollection of what happened. It's a complete shock. He doesn't know whose blood it is, how it got there and what he's going to do next. It's a state of panic for Seth."
Seth also contemplates suicide at one point…
"Yeah, he does - he gets really close to the edge. The whole situation becomes a bit too much for him, he fears that he's killed the stripper and thinks that he can't live with himself…"
"Yes it was, but everyone is really professional on set and everyone will help you out when they can. As I say, it's a lot different from the normal Hollyoaks, because the 6.30pm show is usually a lot lighter, but the opportunity to do something completely different was something that I really enjoyed."
After being at Hollyoaks for over a year, how are you finding it in general?
"It's very enjoyable to work here. All of the people here are great, so I just love coming into work every day. I feel like I've learned so much since I've come here - I don't know how I can explain how much! I wouldn't be what I am today without this job, so I really appreciate all the opportunities that I've been given."
You've been juggling Hollyoaks with sixth form for the past year, haven't you?
"Yeah, I've just finished my A-Levels and got my results a couple of weeks ago! If Seth makes it through the late-night episodes, it'd be nice to give Hollyoaks my all now rather than having to do half and half."
"They're great to work with. Paul Opacic and Kim Tiddy helped me a lot when I first started - they really helped me to settle in, and they taught me a lot that I know today. Rob Norbury and Victoria Atkin have been nice to work with as well, and we've got Jeff Rawle as Silas now too. Jeff's done so much here and it's a privilege to be able to work so closely with him."
Why do you think the Costellos have proved successful with viewers?
"I think we've been privileged to get some of the storylines that we've received, and people seem genuinely interested in what we're all doing and how the characters all work together. As soon as we started, we all gelled off-screen as a family, and I think that really helps as it strengthens the on-screen relationships too."
The family will have to find out the truth about Silas at some point. How do you think Seth will react?
"I think it's going to be an interesting one! Seth really looks up to Silas - he sees him as more of a dad than Carl at the minute, so he's going to be heartbroken when he finds out the truth about what he's been up to…"
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> Read more about the new series of Hollyoaks Later
Hollyoaks Later returns to E4 on Monday at 10pm. Get the Inside Soap magazine on your iPhone or iPad