Marg Helgenberger has revealed she is enjoying playing a sinister character in Under The Dome.

The former CSI: Crime Scene Investigation star has joined the cast of the small-screen adaptation of Stephen King’s novel as Christine Price, a therapist sent to help the town deal with the aftermath of the dome.

Marg Helgenberger
Marg Helgenberger plays therapist Christine Price (Channel 5)

“It’s been a lot of fun because the character doesn’t have a whole lot of rules to abide by, which makes it really fun for an actor because you don’t have to follow any guidelines,” she said.

“It’s just kind of villainous and I haven’t played one of those in a while. It’s a juicy role. I’ve been surprised and I love the edgy stuff they’ve given me to do and I keep saying, ‘Bring it on’.”

The actress said: “Christine Price has this agenda – she is a firm believer in this agenda, which is to get this community to work together and relinquish their selfish needs and desires.

“Her goal is ultimately the right one, her methods aren’t necessarily what most people would agree with. I think she’s doing much more of a heroic thing – not everybody sees her like that though.”

Colin Ford, Marg Helgenberger and Mike Vogel
Marg Helgenberger with her Under The Dome co-stars Mike Vogel and Colin Ford at the 2015 Comic-Con (Paul A. Hebert/Invision)

Marg revealed Under The Dome’s showrunner, Neal Baer, approached her with the part.

“Neal Baer, who I’ve known for many years, had contacted me,” she said.

“They conceived the character with me in mind – the character was originally called Margo but was renamed Christine, which is an homage to Stephen King’s novel.”

Marg Helgenberger as Christine Price and Kylie Bunbury as Eva Sinclair Brownie Harris
Marg Helgenberger as Christine Price and Kylie Bunbury as Eva Sinclair Brownie Harris (CBS Broadcasting)

But she admitted she’s still in the dark over the character’s future.

“It’s still kind of unfolding and I don’t really know how it’s going to ultimately be told, but I’ve got a fair amount of information as to why my character does (what she does),” she teased, adding: “I’m sort of a victim in a lot of ways because of this company, life force.”

Marg, best known for playing crime scene investigator and forensic scientist Catherine Willows in CSI, is throwing herself into her new sci-fi role.

Marg Helgenberger and her CSI co-star William Petersen
Marg Helgenberger and her CSI co-star William Petersen (Reed Saxon/AP)

“Certainly as an actor, it’s fun to do something completely different to what I did before. 22 years ago, I did a Stephen King series called The Tommyknockers,” she said.

“When you’re working in that genre, in a lot of ways it’s liberating because you get to do things you wouldn’t necessarily justify. There are no rules so that’s always appealing and intriguing to me.”

Under The Dome continues at 10pm on Mondays on Channel 5.