Oscar nominee Naomi Watts is one of Hollywood's most in-demand leading ladies but she it's not often she takes on the blockbuster action genre.
But there was a reason she said yes to the dystopian Divergent franchise.
"It's action-driven but it's also female-driven," Watts tells TimeOut during a sitdown in Los Angeles. "And Triss (Shailene Woodley) plays this fantastic young woman who's going through all kinds of challenges and is able to come out on top over and over again and I think it's great for young women to see that."
"I think it's important to have strong female heroines," concurs Woodley. "And I think it's important to have strong male heroes. It's just about finding the equal balance between the two."
Watts plays the scheming factionless leader Evelyn, who first showed up in the second film in the series, Insurgent, and now takes centre stage as a significant antagonist in the third, penultimate, entry in the series. Another draw for the actress was the chance to go bad, something else she's not especially known for.
"I've always wanted to play a villain-esque type character, they're fun," says Watts.
"There's something to do there. It's something to sink your teeth into. Archetypes are always fun and there's an archness to this character and some humour and power and all of those things. It's a good feeling playing a woman who's on top of things... Also she has this complex relationship with her son [Theo James] that she has to resolve. So the mother aspect comes into it too."
Woodley, who's been the driving force of series since the very beginning, has been able to sink her teeth in a character who's evolved drastically over three movies.
"Yeah I think she's very different now," Woodley says of her character, freedom-fighting multi-tasker Triss. "In the first film she didn't know exactly who she was, and in this movie, she's not confined by the restrictions of knowing exactly who she is, but she has a strong grasp of who she is and who she wants to be... When you're at the age that Triss was at when we first met her in Divergent, she was leaving home for the first time, seeing the world outside the perspective of her one individual faction, and now she has a taste of society from a more objective view."
With multiple bombastic set-pieces, including the scaling of a gargantuan wall, Allegiant is perhaps the most action-heavy entry in the series so far.
"We train a little bit, but not too much," says Woodley.
"The great thing about action - when you don't have to be like Superman and show your abs - is you just have to be fit enough to do something for a couple of minutes because you cut, you know, in two minute intervals."
"I didn't have quite those demanding physical sequences that they need, thankfully, I've done my day with that," laughs Watts.
"Not to say that I'm not up for it, but I just don't know, yeah, if the body works quite as well is it used to. That's the good news about playing the older, wiser woman in power. You get other people to do it for you."
There's a prevailing, cynical wisdom in Hollywood that actors must maintain their mainstream appeal by appearing in a franchise like the Divergent series.
"I mean certainly your agents, people, will tell you that kind of stuff, that it's helpful," says Watts. "And there's calculated reasons for thinking that way, but for me, I feel I have to have the material speak to me in some kind of way and possibly grow you in a particular way."
And despite the size of the enterprise, the franchise's lead actress says the commitment has never prevented her from following her own path.
"I was really lucky," says Woodley. "While I've done this series I did Fault In Our Stars, I did a movie last year about Edward Snowden. These films only take three and half months, so we still have time to make other stuff."
That said, the actor isn't in any rush to do another franchise as this one comes closer to wrapping up.
"Never say never, but I can't imagine myself doing that," she says of the prospect. "I'd really like to direct someday. I like real things. I like exploring human interactions. To me Alexander Payne [Election, Sideways] does a great job of really showing human stories. But having them somehow be comedies even though it's a really fucked-up situation. But it's because we're inherently funny in our stressful chaos. We're really funny people. We stress about the silliest things."
The Divergent Series: Allegiant is in cinemas now.strong>