Helen Mirren on the 'Rare' Love Story She and Harrison Ford Tell in 1923: 'The Happily Ever After' (Exclusive)

Harrison Ford and Helen Mirren will admit that they both signed on to 1923 because of the chance to work together again, but their characters' love story helped pull them in, too.

Ford and Mirren play Jacob and Cara Dutton, the matriarch and patriarch of the family and owners of its Montana ranch — the same one Kevin Costner's family will come to own in Yellowstone.

"These two are partners as much as lovers," Ford, 82, tells PEOPLE of his and Mirren's onscreen relationship, to which she says, "Exactly."

He continues, "And [they're] depending on each other for things that they are not part of their quiver of arrows. And it's an extraordinary relationship that Taylor [Sheridan] has written for us to inhabit."

Mirren similarly elaborates on their special onscreen dynamic, which she says is "rare to see."

"In movies, people get married or they meet-cute and they fall in love and they have hot sex or whatever, and then it's all over, happily ever after," she says.

Jacob and Cara's story in 1923 "is the ever after," she says. "Now we're seeing what happens at the end of that story, and you very rarely see that onscreen, but it's actually something that people love to see."

She continues, "They do love to see what does happen in the ever after, if this is a couple who absolutely should be together, are together, fit perfectly well together, and that does happen. That does happen in life."

It helps, too, that the pair get along so well when cameras aren't rolling. "We would sit around together and shoot the s--- off-set," Mirren says.

"She's what we call a broad," Ford says, as he explains, "She's a woman that has the bandwidth to hang with men — not just to be a lady with them, but to actually hang with them."

In season 2, the first episode of which premiered Feb. 23, Mirren and Ford's characters face even greater challenges than before as they fight off both a deadly winter and renewed threats from their peers over their land.

"It gets bigger and bigger," Mirren teases of what's to come throughout the season, as Jacob and Cara's nephew Spencer (Brandon Sklenar) makes his way home to help defend the ranch.

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New episodes of 1923 season 2 premiere Sundays on Paramount+.