In the first episode of the new Wallander series, Kenneth Branagh made sure he wrote the word “smile” on his script. “I figured it was the one opportunity in three films that I get to do it, so I better remember how to move my muscles upwards,” the actor says with a laugh as he mugs a strained smile.

For anyone familiar with the Swedish noir detective from Henning Mankell’s moody and contemplative crime thrillers, the central character Kurt Wallander does very little smiling. A solitary figure with a dogged and singular determination, the seemingly perennially depressed small-town cop solves grisly crimes in a grimly beautiful Swedish countryside. Through nine books, he has become a beloved figure, and while there have been Swedish film and TV interpretations of Mankell’s books, it’s British actor Branagh who has memorably imprinted the character worldwide through a limited television series, the third of which premieres Sunday as part of Masterpiece Mystery.

“There is great affection towards the character,” says Branagh as he sips a cup of hot English breakfast tea on a balcony overlooking the pool at the Beverly Hilton Hotel in Los Angeles after a long day of interviews. “There is no machismo swagger about him. He has this open-wound quality, and he takes all of these crimes personally.”

In the opening episode of Wallander III, “An Event in Autumn,” based on Mankell’s little-known short story The Grave, it seems the taciturn inspector has found peace and contentment with a new relationship and a new house by the sea. That is, until his dog digs up the remains of a human jaw in the back yard, and he becomes obsessed with solving the mystery. “I think he has done some of the best acting he has ever done in this Wallander,” says Rebecca Eaton, executive producer of PBS Masterpiece Series, who also help produce Wallander. “Kurt goes through a big change. It’s a dark emotional journey, but because it’s Kenneth who is so accessible as a warm, smart man, you want to stay with him as he goes through it.”

The much-lauded thespian looking fresh, fit and compact in a neat blue suit, admits it was a character that nearly consumed him. “For the first couple of series, I was pretty isolated and living in a cottage by the sea and seemed to be cold all the time, feeling upset and close to tears, but this third time I have been much better at dealing with it and I was much healthier in myself.”

Branagh who recently received the honor of a British knighthood, has at age 51, become an adept chameleon, easily moving from theater to film to television in front and behind the camera. Nominated last year for an Academy Award for his deft portrayal of Sir Laurence Olivier in My Week With Marilyn, he will next direct a reboot of Tom Clancy’s Jack Ryan franchise, this time starring Chris Pine.

For the working-class Belfast lad, who stripped his Irish brogue early in life to avoid bullying in an English school, he admits that the idea of becoming an actor was more like a revolution than an evolution. But when he burst onto the world stage in 1989 with his gritty film adaptation of Shakespeare’s Henry V, which won an Academy Award and was nominated for two other Oscars, he came under fire, particularly in the British press for his brashness. “My youthfulness was equated with being egomaniacal and it really became annoying to a lot of people, but I was really just a grateful young actor who couldn’t believe that all this was happening beyond my wildest dreams,” he says.

“Somebody said to me the other day, ‘You used to be that Mr. Shakespeare and now you are Mr. Swedish misery,’ ” he laughs. “Maybe I will do a sitcom sometime in the future and then I will be Mr. Smiley.”