Early in her career, critics dismissed Jessie Buckley. She’s having the last laugh

When Irish actress Jessie Buckley eventually appeared for a Zoom interview that she had pushed back by a half hour at the last minute, a patterned headscarf covered her short locks, which looked dripping wet, and magenta bathing suit straps peeked from beneath a loose pink cover-up.

Buckley, who was about to end a six-week stay on the Greek island of Spetses, where she’d been filming Maggie Gyllenhaal’s directorial debut, “The Lost Daughter,” explained the delay. Because she’d be flying back to her home in London the following morning, she’d taken one last dip in the Mediterranean Sea.

“I’ve been waking up every morning at 6 o’clock and [going] for a swim in my knickers before I go to work,” she confessed. “I’ve been reticent to reenter real life, so I’ve been clinging on to fake life.”

Indeed, just before arriving to “Lost Daughter’s” remote, picturesque location, Buckley, 30, had been in Chicago completing her part in Season 4 of “Fargo” after FX’s outsized anthology series had been shut down for five months by the COVID-19 pandemic. In it, she plays Oraetta Mayflower, a nurse with a polite manner, a mincing gait and a habit of murdering her patients.

“She’s sort of an angel of mercy and, on some level, a villain,” said “Fargo” showrunner Noah Hawley, who often found himself marveling over how deftly Buckley wrapped her arms around her complex role, walking the line between farce and drama in almost every scene.

“She was great at even the most absurd things,” said Hawley, citing a vignette where Oraetta gets in a car with Jason Schwartzman’s gangster, Josto Fadda, and engages in a sex act with him while warbling a patriotic American song. “She is literally a dominatrix to Jason’s character and yet she has this veneer of Minnesota nice. You can really go wrong with that. You can go way too broad. But she didn’t.”

The latest installment of “Fargo” is as weird as ever, with thugs, do-gooders and an Oraetta-baked pie that she memorably laces with vomit-inducing ipecac. But Buckley always manages to make her drug-snorting, Edith Piaf-loving character into a living, breathing — albeit terrifying — human being. Her ability to appear totally real, said Schwartzman, is something that seeps into everything she does.

“Physically, she’s an incredible improviser,” he said. “She finds things to do in the scenes that totally affect it and change it. It’s almost like she’s driving the action, like she’s a rudder. It doesn’t even feel like improvisation — it feels like she’s that person doing whatever it is they’re doing in each take.”

Whether portraying a troubled Glaswegian country singer (in the indie film “Wild Rose”); the pregnant wife of a first responder (on HBO’s “Chernobyl”); or a girlfriend who might be a figment of her boyfriend’s imagination (in Netflix’s “I’m Thinking of Ending Things”), Buckley is a super-prepper, throwing everything at the wall and seeing what sticks.

In piecing together Oraetta, whom she thinks of as “a female grim reaper,” she spent three days with a movement coach. “There was something kind of birdlike about her from the moment I first read the script,” said Buckley, who listened to recordings of Minnesotans speaking until the extended vowels of the series’ trademark patois became second nature. “For me, a dialect is like learning a piece of music. Over time, it sinks in. And then you have to forget about it. I don’t like to be too conscious. I just like to be there, you know, chatting with the crew and then [when it’s time] slip back into the world.”

Back in 2008, the judges for a BBC talent show called “I’d Do Anything” didn’t know that someday, Buckley’s ascendance as an actor would require her facility with every sort of accent. On YouTube, Buckley, then 18, can be seen competing for the role of Nancy in Andrew Lloyd Webber’s revival of “Oliver.” Baby-faced and fresh from small-town Killarney, County Kerry, she was championed by Webber for her full-throated singing and star quality but bluntly derided by other adjudicators as “so unfeminine” and “emotionally fragile.”

After the series ended — Buckley came in second — famed theatrical producer Cameron Macintosh (“Phantom of the Opera”) offered to send her to a four-week Shakespeare workshop at the Royal Academy of Dramatic Art. For Buckley, the eldest of harpist/vocal coach Marina Cassidy and bar manager Tim Buckley’s five kids, it changed everything. “Apart from reading it at school and being a bit bored, I didn’t really understand Shakespeare,” she said. “It literally hit me sideways. It felt beyond me and I felt excited by that.”

Not much later, she became a full-time Londoner, singing with a band around town and appearing in a production of Stephen Sondheim’s “A Little Night Music” that began at a fringe 180-seat playhouse but eventually moved to London’s West End. “I got paid 300 quid a week and thought I was a millionaire,” said Buckley.

But her thoughts kept drifting back to her recent brush with the Bard. One night at the Ivy Club, a private venue frequented by celebrities and theater types, Buckley, who’d often show up to belt out a few postperformance tunes, was sitting with Jay Rayner, the food critic at the Guardian and a jazz pianist. “What’s the plan? What are you going to do next?” he asked his young friend. To this day, you can hear the respect in Rayner’s voice when he repeats her answer, that she was enrolling in a three-year program at the Royal Academy of Dramatic Art. “This woman had already come in second in a massive BBC national competition, acquired Kate Winslet’s agent and was in a West End show. That’s all the stuff you do after you’ve gone to RADA. The idea that she’d step away to learn her craft? It was amazing,” said Rayner.

Since then, Buckley’s been nonstop shape-shifting, disappearing so completely into roles that it’s often startling to realize it’s her onscreen. She’s especially eager to begin rehearsals for a new production of “Romeo and Juliet,” starring opposite Josh O’Connor (“The Crown”). Originally scheduled for the Royal National Theatre, Buckley says it’s now slated to be filmed on one of the stages of the venerated performing arts venue, which has been closed due to the coronavirus since March.

Which means fans of “Fargo” will get the chance to see Nurse Mayflower lose her tall white cap and 1950s-era military bob and turn herself into a lovesick Capulet. “I used to say, ‘I can’t act so I change my hair,’” Buckley said, with a self-deprecating laugh. “But maybe it’s working. I don’t know. I like transforming.”