(L to R) Joaquina Kalukango as Camae and Bowman Wright as Dr. Martin Luther King, Jr. in The Mountaintop at the Alley Theatre, which comes to Arena Stage at the Mead Center for American Theater Mar. 29-May 12. (Jann Whaley)

The toilet flushes, and “The Mountaintop” opens with an actor playing Martin Luther King Jr. taking a leak. King sits alone in Room 306 of the Lorraine Motel in Memphis, waiting for his friend “Ralph” to bring him a pack of Pall Malls.

In this room with carpet the color of “bile,” he is not the King with the soaring rhetoric, the preacher man who professed he had been to the mountaintop.

On this last night before his assassination, King is portrayed by playwright Katori Hall as nothing more than ordinary — a man who smokes, likes a little whiskey in his coffee and takes a call from “Mrs. King” while flirting with a hotel maid waiting near his bed.

Hall, a 31-year-old playwright who has burst onto the international theater scene, was not worried in the least about what people might say about portraying King not as an icon, but as a regular man, struggling with his last speech in a dank motel room.

“He had vulnerabilities and fears,” Hall says during a phone interview from her home in Brooklyn, where she has just returned from a trip to Africa to research her next play. “This is a man that provided a fundamental shift in American society. King forced us to see people of color are not second-class citizens; they are equal. He did this extraordinary thing. But he wasn’t superhuman. He always said, ‘I’m a sinner. Not a saint.’ That is the King you will see in ‘Mountaintop.’ . . . It was important to see the humanity in this hero so we can see the hero in ourselves.”

Joaquina Kalukango as Camae in “The Mountaintop.” (Jann Whaley)

When “The Mountaintop,” which opens at Arena Stage’s Kreeger Theater on March 29, premiered in London, critics called her fearless and audiences wondered was this daring young playwright was. The play won the 2010 Olivier Award, equivalent to the Tony, for best new play.

Robert O’Hara, who is directing “The Mountaintop” at Arena, said the rest of the world is just catching up to Hall, whose work includes these 2012 premieres: “Hurt Village,” which starred Tony-winner Tonya Pinkins at Signature Theatre in New York; “Children of Killers,” an examination of Rwandan genocide that opened its American premiere at Castillo Theatre in New York; and “WHADDABLOODCLOT!!!,” which was staged at Williamstown Theatre Festival and featured a well-heeled woman who wakes up one day to find that her crisp New England accent has turned into thick Jamaican patois.

“The recognition of ‘The Mountaintop’ allowed other people to look at her work,” O’Hara said. “She has been been writing all this time. Her mind writes very much in a no-holds-barred type of writing. She starts the play off with King smoking and peeing. If you don’t get up and leave by that time, you deserve what you get. She wanted him to be a real person. King indeed was a heavy smoker.”

Heroes, he said, carry the weight of the world. “Their burdens are great and their demons are large. But we don’t want to actually accept that our leaders have flaws.”

Hall, who grew up in Memphis, admits she is complicated, much like her characters. “I’m very Southern in the way I walk in the world,” she said. “I love to laugh. I love to eat. I love to hug people. But if somebody makes me mad, my neck may roll. I can be aggressive with a Southern twang.”

Her confidence, she said, might be “a little overwhelming to people who think a young woman should say ‘yes’ a lot and be meek. That is the antithesis of who I am. I’m very opinionated, very intelligent and not afraid to show that.”

Hall grew up staging plays in her living room. Her father worked for Kraft, before “he was laid off during one of our many recessions,” she said. Her mother was a phlebotomist. “She took people’s blood,” Hall said. “We jokingly called her the vampire.”

Her mother was also skilled at storytelling. Hall and her four older sisters would gather around the table after the news and listen to their parents recount their day: “What the boss man said that day, or did or didn’t do. My parents would inhabit these people’s voices. It was like watching one-person shows at the kitchen table.”

In elementary school, Katori was admitted to a gifted program that exposed students to the arts. Every other month they would go on a field trip. She was about 10 when she first saw “The Lion, the Witch and the Wardrobe” at a Memphis playhouse.

“It was magical,” Hall recalled.

In 1999, Katori graduated from high school as valedictorian and won a full scholarship to Columbia University. An acting course changed her life: The teacher assigned students to research scenes with characters that looked like them.

“I had an acting partner, a young black woman, just like me, from the South,” Hall recalls. They searched but could find nothing. “When we came back to the teacher, we said, ‘The Columbia library does not have a play with two black women.’ ”

The teacher could not think of a play, either. At that moment, a thought popped into Katori’s mind: “I’m going to have to write those plays then.”

She graduated, then went to Harvard University’s American Repertory Theatre, a graduate training program that includes a residency at the Moscow Art Theatre School. After graduating, she spent two years getting acting gigs in New York — small parts in television’s “Law and Order” — and worked in the communications department at XM radio. “Oprah would come in. Jay-Z and Beyonce. I was surrounded by people living their dreams.”

One day, she wrote “I am a writer” on a Post-It note and stuck it to her computer screen. She overheard her boss telling somebody that Hall should quit and just become a writer. “They would catch me working on plays at my desk,” Hall said. “They needed to fire me or I needed to quit.”

It would be a standoff.

The next week she received an admissions letter to the Juilliard School. “I had only one play, ‘Hoodoo Love,’ ” about a woman who escapes the cotton fields of Mississippi and travels to Memphis to pursue a dream of singing the blues. “Hoodoo Love” was produced in 2007. That same year, she began writing “The Mountaintop,” inspired by her mother’s stories of King.

As a young woman, her mother wanted to go to the Mason Temple to hear King speak in 1968, but bomb threats scared her. “When my mom told me that story, I thought, ‘If my mother was afraid to go to the church, then Dr. King must have been really afraid to go to the church.’ ”

Her mother always regretted not going. The maid character in “The Mountaintop” is based on her. “It was a way to put my mother in the room with King because I knew she didn’t get a chance on April 3, 1968.”

Hall says she “opened ‘The Mountaintop’ in England because the British ‘are used to cracking open the masks of their kings.’ ” After it won the Olivier, “The Mountaintop” premiered in 2011 on Broadway starring Samuel L. Jackson and Angela Bassett.

Hall was still in her 20s. Her rise to Broadway, she said, was surreal. “I feel blessed,” she said. But the play has generated controversy, for — as one critic wrote — taking liberties with dialogue, which is not drawn from King’s speeches or writings. Hall says the play is a magical reimagining of what might have happened that night before his assassination. “I never, ever read the comments below an article on the Web. People are mean. I’m a human being,” Hall said.

She maintains a determination to write plays that interest her. “If you want a play with King on a pedestal, there is a play for you over there. If you want a sanitized version of black women, there is a play over there. I can’t please everybody.”

Halls says she doesn’t write to provoke. “Most of the time, when I’m writing, I’m writing for myself. I’m thinking, ‘What will my character say at this time? What will come out of her mouth?’ I create individuals so real to me, I sometimes start talking to them. Then I let them loose on the page.”

The Mountaintop

runs March 29 through May 12, Arena Stage, 1101 6th St. SW, Washington. 202-488-3300.