Michael Raynor performs his powerful autobiographical play

Whodunit? In many mysteries, that is not only the question, it’s the only question.

In addition to its title inquiry, however, “Who Is Floyd Stearn?” has an even more important question: “Why?”

Written by and starring veteran actor Michael Raynor (whose credits range from “CSI” and “Criminal Minds” to HBO’s “From the Earth to the Moon”), the solo show plays The Smith Center’s Troesh Studio Theater Saturday and Sunday, under the auspices of the Jewish Repertory Theatre of Nevada.

But Raynor’s involvement is far more than professional.

In the autobiographical drama, Raynor tries to conjure a clear picture of the father who abandoned him during his childhood. (Raynor adopted his stepfather’s surname when he turned 18.)

“Who Is Floyd Stearn?” unfolds as “a nonlinear puzzle,” he says in a telephone interview, likening it to “a detective story in style, a ‘Rashomon’-style mystery” in which Raynor portrays not only himself (from childhood to adulthood) but his mother and grandparents, who share conflicting views of his father.

Raynor hadn’t pursued answers to the play’s title question until, playing Apollo astronaut Al Worden in “From the Earth to the Moon,” he found himself in Florida — and mustered the courage to knock on the door of his paternal grandmother’s condo.

He hadn’t seen her for almost three decades; their reunion took place on what turned out to be her 87th birthday.

During the visit, Raynor told his grandmother what he remembered of his parents’ divorce, and “she said, ‘No, that’s not what happened,’ ” he recalls.

Raynor later shared their encounter with his “From the Earth to the Moon” colleagues (including executive producer Tom Hanks), who told him, “ ‘Oh, my God, you have to tell that story.’ ”

And so he began developing the play, which had a successful 2004 off-Broadway run directed by Larry Moss.

That production earned praise from, among others, The New York Times — and radio fixture Howard Stern, who wrote to Raynor to praise the performer’s “insight, charisma and, most of all, courage” in exploring such a “deeply personal story.”

Raynor and Moss reunited to “revisit the story and all the characters” for this weekend’s Las Vegas performances, the director notes in a telephone interview.

In the play, “Michael goes from child to teenager to young adult to middle age,” Moss says, requiring actor and director to determine “the physicality behind” each stage in his life — and each of the other characters Raynor brings to life.

In the process, the actor builds “the vocal stamina, the physical stamina” required for the one-man show, Moss says. “It’s the most difficult thing anyone can do” onstage. (Moss has directed several solo shows, including the award-winning “The Syringa Tree” and the world premiere of Vegas favorite Clint Holmes’ “Jam” at UNLV’s Judy Bayley Theatre; he and Holmes are still working toward “bringing Clint to Broadway.”)

Raynor, meanwhile, has adapted “Who Is Floyd Stearn?” for the screen and plans to direct it once funding is in place — with someone else in his role.

Before “Who Is Floyd Stearn?” becomes a movie, however, the stage version remains, enabling him — and his audiences — to explore “the power of forgiveness,” Raynor says.

And in the process of answering the play’s title question, Raynor’s also learned a few things about himself.

“I learned,” he says, “I had more guts than I ever thought I had.”

Contact reporter Carol Cling at ccling@ reviewjournal.com or 702-383-0272.