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It's been nearly 30 years since Linda Hamilton starred in a Terminator movie, but it wasn't the punishing stunts that hurt when she returned for new movie Dark Fate.

Hamilton is reprising the role of Sarah Connor in Terminator: Dark Fate and facing off with the murderous mechanoid played once again by Arnold Schwarzenegger. The new movie harks back to their previous pairing in 1991's Terminator 2: Judgment Day and opens with digital de-aging that makes them look as they did in T2. It was this scene that brought Hamilton to tears on her first day of filming.

Hamilton was on set that day, but she wasn't actually in the scene. A body double acted as the young Sarah, ready to have a digitally de-aged face added afterward. And Hamilton wasn't keen on Sarah's depiction in the pivotal opening scene.

"Blessings to all, but I just was so upset that I didn't really have anything to do with it," Hamilton says. "Sarah was not putting up the fight that was written in the scene and I'm like no, no, no, no. My body would be doing different things, more fierce. She's not gonna just let him knock her away, she would be biting him, she'd be grabbing his arm -- not that arm, grab the arm with the gun! It wasn't me and it really hurt."

"I cried my eyes out when I got home," remembers Hamilton when I caught up with her in London to talk about the film.

Terminator: Dark Fate is in theaters now. Although it opens with the young Sarah Connor we remember, we soon see the years catch up with the iconic character.

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"I was the one who said I'm coming in with my hair gray," Hamilton says. "Linda Hamilton does not have gray hair yet, but I didn't want to be compared to myself 27 years ago." Hamilton describes the dying of her hair as one of the hardest parts of the movie, bringing it up even before she mentions the difficulty of the many stunts. But it was worth it.

"I wanted people to go, 'Wow, that's not the old Sarah Connor, that's the old Sarah Connor.'"

The non-stop action made the film a real physical challenge for Hamilton, now 63.

"In Judgment Day there was action, but it was basically running away," she laughs. "I think [Dark Fate] would have been hard even if I was the age I was then."

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Both Hamilton and co-star Natalia Reyes, who I also got a chance to interview, single out an underwater action sequence that immersed them in a water tank for weeks and gave everyone ear infections.

"I love the ocean, but this was a lot," says Colombian star Reyes, who previously appeared in Birds of Passage and Lady La Vendedora de Rosas, before making Dark Fate -- her first English-language action blockbuster. "We were shooting from 6 a.m. until 6 p.m. underwater. It was fun in the beginning, but I'm not a fish."

Back in the '90s, Judgment Day pioneered CG effects, but it can't compare with the scale of the visual effects in a modern film like Dark Fate.

"We would shoot a scene and then they would stop so the visual effects guys could come in and shoot the stage and the lighting," explains Hamilton. "I still don't even understand it. There's a guy over there putting pieces of tape on cloth -- for what purpose I have no idea."

The complexity of the action sequences made it tough for the actors to get a handle on where they were supposed to be in each scene. "It's the first script I've ever read that I didn't fully comprehend, because there's so much action going on," says Hamilton. Fortunately the cast kept up by looking at the previsualization, or previz, which is an animated version of what the final movie will look like. "Previz saved our asses," she says.

One side effect of the effects-heavy production is that everything is meticulously planned in advance. Does that leave room for improv? "Nope!" laughs Hamilton -- unless you're Arnie, who added or changed some of his lines.

Now playing: Watch this: Terminator: Dark Fate cast geeks out on Linda Hamilton

Hasta la vista, baby

Alongside Arnie, a new Terminator is played by Gabriel Luna as the series ventures to Mexico. Reyes is pleased her Mexican character is a regular hard-working person rather than a stereotype involved with the drug trade or crime.

"I do feel we've been misrepresented and under-represented, not only in Hollywood," she says, before highlighting a recent study revealing that the number of Latinx characters in film and TV lags far behind the actual proportion of the US population.

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In one sequence the Terminator pursues our heroes across the border into a detention center, where director Tim Miller penned the cast and extras behind fences.

"Our director was crying," remembers Reyes. "We hear about it in the news. But when you actually see people in cages, being treated in such an inhuman way when they just want a better life -- It's really important to talk about this, and to try and see the other as another human trying as hard as you are."

Artificial intelligence and angry robots aren't trying to kill us yet, but there are plenty of urgent issues affecting us right here in the present. Reyes is particularly passionate about fracking in her native Colombia. "I worry about climate change," she says. "It's not science fiction. It's not something we should worry about in the future. This is an emergency, right now."

Originally published Oct. 22.