When Shalita Grant, who portrays the soothsayer Cassandra in "Vanya and Sonia and Masha and Spike," took part in an early reading of the work last year, she asked the playwright, Christopher Durang, "What do you want me to do?" In an interview the other day, Grant told me: "He said, 'I don't really know what this is yet. Just try some stuff.' Okay, I thought. I decided to go hard or go home." 

It didn't take long for Grant to come up with an interpretation. "I thought of my great-grandmother. She's bipolar. When she's not on her meds she becomes an evangelist. Trying to convert not just people but things. For example, she will stand in front of my grandpa's house and sing and dance to bless his home. Or she'll come and talk to him for hours while he's trying to work on his car." 

Grant, who grew up in Petersburg, Virginia, and in Baltimore, where she attended an arts high school before enrolling in the drama division at Juilliard (class of 2010), has an entire repertoire of such family lore. But since in "Vanya" she channels her great-grandmother I urged her on in that direction. "My first funeral was when my great-grandmother's mother died," she said. "I was nine. My great-great grandmother was a bootlegger. She had an illegal bar in her home until the day she died. She was really mean and often drunk. 

"So there we are, sitting at the funeral, when, at the back of the room, there's a commotion. I wheel around and see my great-grandmother making her entrance. She's wearing a gold headress and a gold dress. She walks right up to the pulpit. She pushes the funeral-home director out of the way and proceeds to speak. She doesn't give a standard eulogy but talks crap about members of the family, who are present. Stuff like: 'You're ugly because your daddy was ugly.'"

Grant continued: "Keep in mind that I'm only nine at the time, so I was pretty freaked out. But no more so than when my great-grandmother did a costume change -- from all-gold to all-silver -- in time for the burial. Just before her mother is going to be lowered into the grave, she opens the casket and plucks the hat off the corpse, hissing, 'I only let you BORROW this.'"

That many of the women in Grant's family have had what she calls "crazy lives" has contributed to her work as an actor beyond the "Vanya" play. "Already when I was very young they were sharing their struggles with me," she said. "I was forced into being a good listener, and being very observant -- the kind of things that are useful to you as a performer." Grant said she also benefited from her family's tough love. "I spent the first ten years of my life trying to get my family to laugh at one of my stories. My aunt, who's five or six years older than me, would constantly amuse people, but I didn't have much success. I'd tell a story and they would say: 'That's not funny, get to the punchline.' It was good preparation for being reviewed, both in drama school and by critics." 

Grant said she finds whispers of something from her family life even in Shakespeare: "I should say: especially in Shakespeare. I connect more to him because of how out-there a lot of my family members are. Shakespeare is very real to me." 

What about Chekhov, who inspired Durang to write the "Vanya" play? "I joke a lot with Liesel Allen Yeager, who understudies Nina in this play and who was part of my group at Juilliard. She says that she can't do Shakespeare, because her family is always stewing and tends to be quiet -- they're more Chekhov. Not my experience!" 

Yet Grant is living in a Chekhovian universe for another month. "True," she replied, "but I'm sort of the ancient Greek chorus in the middle of all this." And does she have background in that genre? "Oh, yes," she said. "As a teenager, I gravitated toward the Greeks. Euripides, Aristophanes: I love them. I did 'Lysistrata' in high school, for God's sake." 

But mostly, Grant kept reminding me, her Cassandra is an act of mirroring the great-grandmother. "She's a very angry woman, so in rehearsals we had to keep track of that emotion. Nicky Martin" -- the director of "Vanya" -- "was a big help there. He helped me to make sure we found the joy in the character." 

Brendan Lemon is the American theater critic for the Financial Times and the editor of lemonwade.com.