As the final Homeland season begins (Sunday, Showtime, 9 p.m. ET), one scene seems to define the fictional Carrie Mathison and the very real Claire Danes (top), who plays her.

Carrie, a CIA agent, is back from months of isolation and torture. With her mind and memory shattered, she's in slow recovery; then there's a question: Does she want to go back in the field right now?

Her answer is an instant yes. That's also Danes' answer to returning to a draining role.

"It's taxing," she told the Television Critics Association (TCA) last month. "It's kind of pummeling." But she came back for this eighth season, even after her original commitment had finished.

"I'm so intimate with this imagined person now," Danes said. "And I've been carrying her with me for almost a decade."

She's taking Carrie to the show's finish, which is a little like the start.

In the first three seasons, questions swirled around Nicholas Brody (Damian Lewis), a former prisoner of war. Many considered him a hero while Carrie worried that he was a traitor.

And this season? "Carrie Mathison steps into Nicholas Brody's shoes," said Alex Gansa, who co-created Homeland, adapting it from an Israeli series. "She's the one who's under suspicion; she's the one whose loyalties are questioned (even by) herself because her memory is so fragmented."

It's a demanding finish, for a character who has always been complicated.

"When the pilot of Homeland was written, Carrie Mathison was not bipolar," Gansa said. That's when Showtime officials asked him "to push the boundaries of the character."

Carrie was keeping her condition secret – while trying to uncover Brody's secrets. As Danes recalls it: "She had something that she was hiding…. I was just so relieved when I got this script to find a character who was driving the story forward."

Danes had been a teen Emmy-nominee in My So-Called Life and soon drew raves from top directors. Steven Spielberg called her "one of the most exciting actresses to debut in 10 years," and Baz Luhrmann called her "the Meryl Streep of her generation."

She did a lot of fairly good roles and a few great ones – including Luhrmann's Romeo + Juliet (1996) and her Emmy-winning role in Temple Grandin (2010).

And then, oddly, she hit a two-year lull.

"I was so inspired by that (Temple Grandin) role and so challenged by it," Danes told the TCA in 2013. "I felt like I really had to push myself…. I didn't have patience for regular old stuff."

For a while, she said, that's all that was available. "There was kind of a dearth of material…. But it all worked out."

She found Homeland and has won two Emmys as Carrie, whose life was teetering. "She can't take her sanity and her health for granted," Danes said. "She knows that things can go boom. They can go wrong really, really fast."

It's a role that drains energy and batters the psyche. And yes, Danes was ready to do it again.