The only thing more compulsively mesmerizing than one famous person is two famous people in love. The cultural fascination with celebrity couples isn’t complicated; they are our own relationships writ large, and sparkly. There are the transcendent portmanteaus (Brangelina, J-Rod), the industry mergers (Kim and Kanye), the legends (Jackie and JFK), the star-crossed lovers (Katharine Hepburn and Spencer Tracy), and the ones who yield whole families of fame (Will and Jada and Willow and Jaden). There are the conscious uncouplings, the cheaters, the fighters, the ones who get back together.

And there are Rose Byrne and Bobby Cannavale, a power pairing of talent and—if you ask anyone on the internet—duplicative hotness, all the more tantalizing for the privacy in which they shroud their relationship and how, yes, “just like us!” they can seem. They do projects together again and again and again, though they don’t do press as a couple. They don’t do much press at all. They are rare. They are enigmatic. They are here with us this morning, for tea and breakfast in a Toronto café.

“I mean, it’s not something we do all the time, but we’re trying to go with the flow,” Byrne is telling me, cutting her eyes at Cannavale, who’s settling into the chair next to her. “We’re generally pretty private.” I know, Rose! I know!

In the seven years they’ve been a couple, they’ve worked together five times and are about to make it two more. She was a bright-eyed assistant and he a sleazy political flunky in the 2014 Annie remake; she the sadistic daughter of a Russian arms dealer and he a terrorist middleman in the 2015 Melissa McCarthy vehicle Spy. Recently, they were lovestruck beasts in Christopher Weekes’s short Martha the Monster, and in one episode of the zany Rashida Jones series Angie Tribeca, Cannavale’s large-adult-son character becomes smitten with Byrne’s Wall Street bigwig Norrah Newt. They even played a married couple on the rocks in the indie comedy Adult Beginners: Cannavale’s character sitting beside Byrne’s during an ultrasound appointment, Byrne’s character telling Cannavale’s “I lah you” through a mouthful of toothpaste. A fight, a smooch, a sleepy airing of grievances side by side in bed. Indeed, one would be hard-pressed to think of a romantic partnership with such fruitful onscreen output since Taylor and Burton.

“It starts out as a very pragmatic thing,” says Cannavale. “You have the kids, the kids are getting bigger, and you don’t want to spend the time apart.” Given that much of their joint work was done before the birth of their boys—Rocco, almost four, and Rafa, two—it’s possible that they also just enjoy working together. Byrne was the one who, when approached for Adult Beginners, suggested Cannavale for the role of her character’s husband; by happy accident and some subtle machinations on the part of the story’s creator and star, Nick Kroll, the part had been written with him in mind.

But it’s true: The travel is hard. They moved to Brooklyn’s Boerum Hill neighborhood in 2016, three days before Rocco was born, and have spent the intervening years on extended work trips to sets in Atlanta, Los Angeles, and Sydney. Now they’ve taken up temporary residence in Trinity-Bellwoods, which Cannavale calls the Brooklyn of Toronto, while Byrne shoots the FX miniseries Mrs. America, about Phyllis Schlafly’s campaign against the Equal Rights Amendment. She’s playing Gloria Steinem.

Australia-based productions are particularly attractive to Balmain-born Byrne, whose parents retired to a garlic farm in rugged Tasmania. In 2016, she appeared in the Sydney Theatre Company’s Speed-the-Plow; next winter she and Cannavale will return to star in A View From the Bridge. “I don’t know if you’ve heard,” Cannavale says, “but that flight is crazy long and expensive, so we’re always trying to find somebody to pay for us to go.” Here, Byrne deploys her platonic ideal of a laugh, an infectious ha ha ha! He is joking, after all. Mostly. It doesn’t hurt that the Arthur Miller play is bucket list material.

So they’ve worked together, sure. But they’ve never done anything quite so emotionally probing as the psychological thriller they’ll star in this January at Brooklyn Academy of Music, a limited run of writer and director Simon Stone’s Medea, which blends the brutal Greek classic with the real-life story of Debora Green, a Kansas physician who poisoned her husband and killed two of their children in a house fire in 1995.

“You hear the word Medea and you’ve already prepared the audience,” says Cannavale. Even if the details are hazy, “everybody knows how that story ends.” It’s a horror story that can read as a revenge tragedy, a cautionary tale of love gone wrong, a proto-feminist war cry, or some amalgam of the three. As soon as he picked up Stone’s script—which transmutes Jason and Medea (the mic drop of celebrity couples) into Lucas and Anna, estranged spouses and former colleagues at a contemporary research lab—Cannavale says, with pleasure, “I was filled with this sense of dread.”

Byrne’s apprehension was more existential. “We’ve never done anything like this. I’ve never done anything like this in my whole life,” she says. “That role is in the canon of the greatest roles for women ever written. And it’s historical, it’s mythological, it’s also current—working with my husband…. It’s exciting, challenging, terrifying. But that’s why I’m doing it, you know?” (Though Byrne wears two bands on her ring finger and calls Cannavale her “husband,” their representative informs me that they are not legally married “as of yet.”)

“She had a little bit of paranoia around the impact it would have on her psyche,” says Stone. Besides the dark aspects of Anna’s character, the lead roles push Byrne and Cannavale, as co-parents themselves, toward an uncanny valley. There’s a frisson in watching two actors mimic a version of the relationship they actually share—Jane and Henry Fonda in On Golden Pond, Emily Blunt and John Krasinski in A Quiet Place, Will and Jaden Smith in The Pursuit of Happyness, Cannavale himself on Nurse Jackie, playing a father to his actual 24-year-old son, Jake, whose mother is the award-winning screenwriter Jenny Lumet, Cannavale’s ex-wife. But for the couple, that tension takes on a particular gravity when the story arc involves infidelity and murdering one’s children. It wasn’t those sensational aspects that most interested Stone, however: He wanted to explore complex domestic dynamics with a couple who had their own history.

Theirs is a case of opposites attracting: Joe Lo Truglio, Cannavale’s best friend since high school, describes him as the high-strung rainstorm to Byrne’s relaxed cumulus cloud. Their career paths too are starkly distinct. “Rarely do you find two people who are equally talented and unique and singular voices in their space, who work well together—and in such a variety of projects,” says their former colleague, Nick Kroll.

Cannavale is the New Jersey-born son of a divorced Italian-American chemical plant worker and a Cuban social worker; he spent his adolescence bouncing through the homes of family members in Jersey’s Union City; Puerto Rico; and Margate, Florida. After scraping together a high school diploma in the wake of expulsion, he spent years working up to roles on Will & Grace, Vinyl, and Boardwalk Empire. His recent films include I, Tonya and The Irishman. But he describes feeling like a racehorse pawing at the starting gate between takes, and the theater will always be his first love. “He is incredibly masculine and has a very big physical presence, but he’s also really fucking smart, and there’s always a wit and a vulnerability to his characters,” says Daniel Radcliffe, his 2018 costar in The Lifespan of a Fact.

Byrne says the immediacy and vulnerability of the theater are a challenge for her, though you wouldn’t know it. In the 2014 revival of You Can’t Take It With You, her Broadway debut, she elevated her typically flat foil of a character into a hilarious locus of anxiety, raking her hands through her hair until she looked electrified. “She never let you catch her at it,” says James Earl Jones of his experience working with Byrne in the play. “It was not something she did. It was something she became.” Byrne was raised in the suburbs of Sydney, the youngest in a tight-knit quad of children, her parents a statistician and an elementary school administrator. Public high school; local university. After a spate of dramas like The Goddess of 1967 (in her stunning performance as a blind teenager and victim of sexual assault, she vacillates between naivete and wild catharsis) and her five-season Damages run, she carved out a niche as a straight-faced scene-stealer in a slew of popular comedies—Get Him to the Greek, Bridesmaids, the Neighbors films.

Glenn Close, Byrne’s Damages costar, says Byrne “had something so much more than the kind of acting one was seeing on TV at the time.” She says Byrne has “great courage” and isn’t afraid to take risks, but that her most obvious gift is her ability to make people laugh. It was during the Damages years that Byrne and Cannavale got together, introduced by a mutual friend. “The chemistry between them, it’s just so remarkable,” Close says. Plus, “they’re both kind of universally loved.”

In Toronto, they’ve been spending time at Artscape, a free arts hub and farmers market, and on weekends the cast of Mrs. America—which includes Cate Blanchett, Uzo Aduba, Tracey Ullman, and Sarah Paulson—can often be found at their house, hanging out. But Medea will bring them back to the place they love most, the Brooklyn of New York. Cannavale misses the long-standing weekly poker games he plays with fellow card sharks Jon Hamm and Paul Rudd. Byrne misses the galleries, the art shows. They both miss the theater.

When Byrne calls Cannavale her “biggest champion” in deciding to do Medea, she’s very serious, almost reverent. “He was like, ‘We should do this. This is exciting. You know—this is 10 minutes from our house.’ ” Ha ha ha! A gallows banter is in effect. “Don’t kill the kids,” says Cannavale in a meditative chant. “Don’t kill the kids. Don’t kill the kids.” “Yeah, I’m just going to take some really heavy drugs,” says Byrne. “Take the edge off till it’s all done.”

Humor seems to be their love language. When I ask if they’ve noticed a gendered difference in how they’re treated, Byrne says, “Yeah. He’s getting hit on all the time. I’m like, ‘I’m fine. I’ve never had anything like this situation.’ ” “I have been objectified all the time,” says Cannavale, grinning. (It’s true: “Bobby Cannavale Is Objectively a Sex Symbol” is a respectable publication’s take on the matter.) They revel in a certain script-flipping. Cannavale proudly points out their income disparity. “I make half as much as she does,” he says. “Down the middle. Half. I work too much in the theater, perhaps.”

#MeToo has prompted more sober discussions. “I don’t know where I fall on the things that I’ve enjoyed creatively but are now being ‘canceled’ because of terrible stories about the director, the actor,” says Byrne, who starred in the indefinitely postponed Louis C.K. project I Love You, Daddy, which premiered just before multiple women accused C.K. of sexual misconduct. But Byrne supported the decision to cancel the film’s release and condemned C.K.’s surprise comedy sets in late 2018.

She continues what is clearly an ongoing conversation in their house: What to do with the art of unfavorable makers? “Michael Jackson,” she puts forth. “He’s in the molecular structure of music.” Cannavale chimes in. “We’re not in opposition with these things,” he says. “I’m learning. Sometimes I’ll say things that she doesn’t agree with. I’ll go, ‘Well, I don’t know if I can just cancel all of Woody Allen’s movies in my head.’ And so we might get into an argument about it.” (Cannavale starred with Blanchett and C.K. in Blue Jasmine, Allen’s 2013 twist on A Streetcar Named Desire.) But the friction feeds the work, they agree. These discussions are the bedrock that will allow them to attack what Cannavale calls the “nuclear” material of Medea. One thing Cannavale’s certain of: “I don’t want anybody to tell me I can’t tell a story about somebody who is controversial, or I can’t portray somebody who is morally conflicted. Those are characters we need to be able to see in order to understand the larger—” he slows down, searching for a word. “The human condition,” Byrne supplies.

In A View From the Bridge, they’ll play married couple Beatrice and Eddie, who becomes infatuated with Beatrice’s teenage niece. Following Medea with another fraught marital dynamic will be “interesting,” I hazard. “It’ll be distressing, you said?” Cannavale asks. Byrne, delighted, proclaims the misunderstanding Freudian. One can only imagine the discussions the play will prompt “at 9:48,” Cannavale says, “10 minutes before we shut the lights off and go to bed.”