From the moment the credits roll at the start of Pure Mule: The Last Weekend, it's clear that the tone of this follow-up drama is distinctly more sombre than its predecessor. In the original, justly acclaimed six-part drama that was first aired in the autumn of 2005, it was the devil-may-care hedonism of a boomtime Midlands town that raised eyebrows and drew attention to the antics of a generation that had known nothing but affluence.

The arch bad boy of the piece was Scobie (Garrett Lombard), the cocksure but vacuous ladies' man who lived it up like there was no tomorrow, but in Pure Mule 2 he seems a somewhat diminished figure. Once an overpaid building-site labourer, he's now reduced to working nights as a security guard on an unfinished housing estate, and is about to emigrate to Australia in search of work.

But just as Scobie is about to leave, trouble looms in the shape of Jennifer, Scobie's ex, who's back from England for her mother's funeral but isn't long in causing a ruckus.

Among the many merits of the excellent original series was the performance of a then 20-year-old Charlene McKenna, who was a revelation as the unstable, impulsive Jennifer. Since then, she's capitalised on that early success with a string of memorable performances that have made her perhaps the most promising young Irish actress of her generation. But all her subsequent achievements didn't make the actress any less nervous when she heard that writer Eugene O'Brien and director Declan Recks were planning a sequel to Pure Mule.

"I was really thrilled when one of the producers called me last Christmas and said they were thinking of it," she tells me. "But I suppose I was a bit scared about whether or not the demand for it would be there, whether people would still care about the characters.

"Also, there's a very fond place for Jen in my heart -- it was one of my first leads, and I loved the show. So, in a way, I was scared to go back to her because I wanted to make sure that I could still capture the essence of her. But the shoot was great; it was great to go back there and film in all the same places, but this time without Tom [the actor Tom Murphy, who sadly died in 2007], which was very sad, so it was a very emotional experience in many ways, both high and low."

In the new show, things have moved on for Jennifer. "At the end of the first series she went away to England, with the head held very low! And now, four years later, she's back for her mother's funeral with a very lovely, wealthy Englishman in tow, which is a big difference for her: the last time she came back with a didgeridoo; this time she's got a man."

McKenna, who now lives in London, found it easy to relate to the show's homecoming themes. "Jennifer has gone on this great journey and she's evolved, then she comes back to somewhere that hasn't really changed. Going home like that always brings something out in you, and it's that old meets new and what evolves from there, set against her mum's funeral and recessionary Ireland."

Recession is very much to the fore in Eugene O'Brien's drama, as several of Pure Mule's fictional town's pubs have closed down and the characters are feeling the economic pinch like the rest of us.

"I think Eugene has caught the mood of the moment very well, but he's great at that anyway. He's great at telling it like it is and calling a spade a spade. In his scripts you've nothing to change, you're not reading it going, 'Oh well, I can make that work'. He writes perfectly -- every comma, every beat. It makes it very easy for an actor to do her work well."

For Charlene, now 25, O'Brien's ground-breaking drama was an important stepping stone in a rapid rise to the top of her chosen profession. But it's a career path that was pretty clear to her from early on. She hails from Glaslough in Co Monaghan, where her family owns a pub.

"I started doing Irish dancing when I was four and learning the piano from about six, so there was performing there but it's not in the family -- no-one else has done it, and I still don't know where it came from or why I loved it."

But love it she did, and she shone in an amateur production of Oklahoma! at the age of 11. She grew more involved in amateur theatre as a teenager, and landed her first professional job at the age of 16. "It was a Swedish kids' TV show," she laughs, "for which I had to be frightfully posh. The idea was to teach them English, not Monaghan English, which would have confused them. There would have been some very strange accents from the kids in Sweden!"

When Charlene finished school, she went to college to study to be a teacher, but fate had other plans in store. When Neil Jordan's people spotted her in a production of Romeo and Juliet, she was asked to audition for a part in Breakfast on Pluto.

"I went and met Neil and Cillian Murphy and I read for the part. Neil said 'Yeah', and I thought, 'This is how it's always going to be, just meet the stars and off we go'. Didn't turn out like that, of course."

All the same, it was Breakfast on Pluto that earned McKenna an audition for Pure Mule, and her eye-catching performance on that show would open many doors. Small roles in films such as Middletown (2006) and Small Engine Repair (2006) were followed by larger parts in the crime drama Single-Handed (which has recently been reshown in Britain on ITV and gained high ratings) and Whistleblower, the powerful dramatisation of the gynaecological scandal at Our Lady of Lourdes Hospital in Drogheda in the 70s. Her performance as a young mother who's subjected to an unnecessary hysterectomy won her widespread praise.

And then there's Raw, the steamy drama set in the kitchens of a high-end restaurant, which will also be returning for a new series in January. "It's much weightier this time," she says. "We've heavier storylines, we've tackled some big issues, and it's seeing someone like Jo-Jo being forced to grow up a bit -- it's not all fun and games."

As we mentioned earlier, Charlene is now based in London and is looking forward to expanding her career there, and elsewhere. "I'd love to work in America," she says, "but I'm in no mad panic -- I don't want to run before I can walk, and all that."

Meanwhile, there's the new Pure Mule, and while Charlene admits that "the pressure is on" in terms of matching the original, she believes they've made "a fantastic show, and I hope that fans of the first series are happy with it, because we are. I'm proud of it".

Pure Mule: The Last Weekend screens on RTE1 this Sunday and Monday at 9.30pm

- Declan Cashin