The 1963 Ku Klux Klan bombing of Sixteenth Street Baptist Church in Birmingham 50 years ago claimed the lives of four young girls.

One of the girls who died was Addie Mae Collins, a friend of Marie Hall. The murder of her friend and the other girls has motivated Marie Hall Mullen, a Western New Yorker since 1968, to share her gift of writing with an audience. On Saturday, Mullen will direct and appear in her play, “Sit Down Servant, Vengeance Is Mine,” at Mount Olive Baptist Church.

“It’s my past that calls me to do all of this, and the bombing of Sixteenth Street Baptist Church,” says Mullen. “I can’t let [Addie Mae Collins’] death be in vain, I will not, I’ll die trying.”

Mullen left her hometown of Birmingham in 1968 when her then-husband came here for work. But it was more than just economic opportunity that brought the couple North. “There was such civil unrest in Birmingham at the time, and I just wanted to get out of Birmingham,” she says.

Mullen raised two children and studied education at Buffalo State College while pursuing her creative interests. She designed clothing and hats, and ran her own company, Just Ree II, as well as working at Calspan for many years.

An avid writer, reader and public speaker, she volunteered with Literacy Volunteers and as a high school debate judge, and was active in Toastmasters.

But Mullen didn’t talk much about the attack that killed her friend and the three other girls until 2006, when, she says, “they were burning churches in the South and Coretta Scott King had just died, and I thought, ‘You need to unload this. You need to start talking about what has happened.’ ” Now, she says, “It’s really coming out in my work.”

“Sit Down Servant” is the first play in a trilogy Mullen calls “Miss Tessie’s Legacy.” Set in Tippah, Miss., and in Buffalo in 1860, the play has a cast of 24, ranging in age from 9 to their 70s – all participants in the Mount Olive Baptist Church Theater Workshop. The play also features several songs, including some spirituals that were sung during the 1860s.

Paul Denning has done some historical research for Mullen’s plays, including writing footnotes for the programs, and he plays an abolitionist minister from Buffalo, Bartholomew Caldwell. The fictional character is based in fact – Western New York was the home of many abolitionists and Underground Railroad conductors, he points out.

“We’ve got a great cast,” Denning says. “There are only a few white characters in the play and it’s interesting to be one of them, to be helping the people in slavery, although it’s a challenge to be accepted by some of the characters. It’s a good part.”

Mullen says the character she plays, Miss Tessie Jackson, “is free only because people think she’s off her rocker.” Miss Tessie, who was once jailed after clashing with the richest plantation owner in the South, “is not a fun-loving character, she is a downtrodden character,” says Mullen.

The play does not gloss over the horrors of slavery. Miss Tessie and her brother Ebenezer have seen their father being brutally beaten and then sold. And a powerful auction-block scene, set just before intermission so parents can take their children out if they prefer, “is a horrible scene,” says Mullen. “You will see people crying as a family gets up on the auction block and is about to be separated. When we rehearsed it, other members of the cast were watching, and tears were just streaming, even down men’s faces.”

Ebenezer Jackson flees slavery and heads north at age 12, but Miss Tessie stays. Three children whose parents have both been sold off seek refuge at her house, and she takes them in. An unexpected letter from an unlikely source brightens a desperate situation.

Although some parts of the drama are difficult to watch, Mullen says it’s vital to educate young people about what their ancestors suffered.

The play, which is the first in the trilogy, is narrated by storyteller Sharon Amos. It was staged three years ago at Mount Olive, followed by the second and third plays in the series, “Bittersweet: The Broken Promise,” and “Across the Waters.” Mullen says “Sit Down Servant” is “being brought back by popular demand.”

The cast has been rehearsing since September, and Mullen is happy with the way the drama is being interpreted. “I was watching them at rehearsal, and I am working with some talented people who can tell this story the way this has been written,” she says.

The 90-minute play starts at 4 p.m. Saturday at the church, 701 E. Delevan Ave. It is free and open to all, with no tickets required, although seating will be limited.