Marcus has only ever been in relationships with men, but when he shares an unexpected kiss with Maria in tonight's (October 5) double bill, he is left questioning what he wants from his future.
Despite currently being in relationships with Aiden Lester and Jason Grimshaw respectively, Marcus and Maria will ultimately decide to make a go of things as a couple - but will they really have a happy future together?
Digital Spy recently chatted to Charlie Condou, who plays Marcus, to hear his take on what's in store.
What was your first reaction when you heard about this storyline?
"Well, they first told me about it a really long time ago. It was probably over a year ago when they spoke to me and Sam about it, so we always had an idea that it was coming. I think we were both a bit surprised!
"Certainly, the one thing I can say for Marcus is that he's a gay man who's very comfortable with his sexuality. He isn't bisexual, so I was worried that they were going to suddenly take the easy option and say, 'Oh no, Marcus has had girlfriends before Sean - we've just never talked about it!'
"That was the thing that worried me most, because I thought that would have been the coward's way out when it comes to looking at this situation. But our producer Phil is gay and some of the writers working on the storyline are too, so they assured me that they weren't going to mess it up.
"What they told me was that they just wanted to look at what happens when two people fall in love and their sexualities are so different. So after that, I was really interested to see what would happen."
Even before it's properly kicked off, the storyline has become a talking point among fans. What kind of a reaction have you seen so far?
"I haven't really looked at the forums, but on Twitter I've had quite a nice response. But then of course, that's only the people who are tagging me into their tweets - I wouldn't know what anyone else is saying!
"I think a lot of people will probably be quite confused by it, but what I would say is that nobody is more confused than Marcus and Maria. If they had the kiss and then all of a sudden they said, 'Oh we're together now, why is everyone confused by it?', I think I'd have a problem with the storyline. But that's not the case - they're still really confused by what's going on.
"They're trying very hard because they really love each other, but I think there's going to be a lot of problems down the road. That will ultimately be because of Marcus's sexuality. And for anybody that has doubts about the storyline, I'd say just be patient, stick with us and watch where it goes."
We've seen that Maria has had feelings for Marcus for a while. Has Marcus been thinking along the same lines too?
"I genuinely don't think he has - it's something that he just hasn't considered before the kiss happens. We actually played a scene recently where Marcus said to Maria, 'This is never going to work, I'm gay, I've always been gay - end of story'.
"But I think Marcus realises that he does have really strong feelings for Maria and that it is love, so he feels like he's in a bit of a catch-22 situation. He's in love with her and even though he doesn't really understand it, there's not really anything he can do about it. So he makes the decision to go for it, and see where that takes him."
Marcus has been dating Aiden for a little while, so does he feel guilty?
"I think he feels incredibly guilty. Aiden was perfect on paper - he's good-looking, he's got a great job, he's a kind man and he's a grown-up, which Sean definitely wasn't. But while Marcus was very much in love with Sean, I think there was always something missing with Aiden. Even if he hadn't fallen in love with Maria, I'm not sure whether Aiden was really the one for him."
You mentioned that Marcus isn't bisexual, so do you think Maria is the only woman he would fall for in this way?
"Well you can never say never, as you never know what is going to happen in a soap - the same as in real life. But I don't think this is a new beginning for Marcus, and I don't think you're going to see him working his way through the female residents of Coronation Street!"
Is it Maria herself that Marcus loves, or just what she can offer him in terms of a family?
"I think he's definitely in love with her - or at least, he thinks he is. But I think more than anything he's just incredibly confused. Part of what drives Marcus is his need to be part of a family and his desire to have children. That's a big part of who he is, and I think he tried doing that with Sean and didn't get anywhere.
"He's got so close to Maria that maybe things have got confused for them. But certainly at the moment, he feels like he's in love with her."
Is it true that this will be a long-running story for Corrie?
"Well, they certainly haven't talked to us about an ending to it yet. We usually only find out our stories a few months ahead, and at the moment we're still very much together. But who knows? This is Coronation Street, and I can't imagine that things would ever run smoothly in soap!"
Are you enjoying working so closely with Samia?
"Yeah, we're really close friends, and that's what's been so lovely about the storyline. Sam and I have been mates since I started on the show, and she is definitely one of my favourite people to work with. It's been an absolute joy - she's always on time, always knows her lines and is always brilliant in the scenes that we do. I couldn't have been happier that they've given us so much to do together."
Are you pleased that Marcus splitting from Sean seems to have broadened his horizons as a character?
"Yeah, I think I am. It's always difficult when you come into a show and you end up being with someone who is so well-established. I think in a lot of ways I suffered from that - I never felt like I was able to spread my wings.
"I always felt like I was part of Sean's storyline, which was great for a while, but was starting to become less interesting for me. When Phil asked me to extend my contract a year or so ago, we talked about where Marcus would go and they said they had lots of ideas. Those ideas are coming into play now, so I think it was good for Marcus and Sean to split up. I feel like a character in my own right now, which is great."
How will Sean react when Marcus and Maria get together?
"I think it's obviously going to be a massive shock for Sean. That's the thing that's really interesting about the scenario - everyone's confused by it and nobody can work it out. It's going to be really tough for Sean, and he does have a tendency to make everything about himself anyway, so there'll be a lot of that going on!
"It's also going to be really hard for Jason, of course. There are also other people on the sidelines of the storyline like Eileen. She's good friends with Marcus, but she's Jason's mum. So there'll be a real conflict for everyone. It's amazing how it has a big effect on a lot of people on the street."
When you returned to Corrie last year, did you expect to stay around for this long?
"Well, when they first asked me to come back, it was for a really particular storyline - it was about bringing up Dylan with Sean for a short period. I just found the whole idea quite interesting, not least because I'm in a similar situation in real life with having kids and being a gay man.
"At that point, I didn't really think about it any further than the three months I was contracted for. It was only afterwards when Phil called me into a meeting and said he'd really like me to stay."
The last we heard was that you'll be sticking around until March 2013 at least. Would you like to stay on beyond that?
"Oh, if the storylines keep coming I'll stay on forever! This is without a doubt the best job that I've ever had. The people here are amazing - the cast and crew - and I'm a huge fan of the show myself.
"Moving forward, I'd like to see a little bit more of Marcus's dark side! Often he's always saying and doing the right things, and that can get a bit boring after a while. But I think in this new storyline with Maria we're going to see a lot more conflict - and probably him not behaving in the best way possible! As an actor, that's a lot more interesting to play."
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Coronation Street airs Mondays, Wednesdays and Fridays on ITV1.