Was it the professor in the conservatory with a lead pipe? The colonel in the ballroom with a revolver?
The brain-stretching effort in piecing together a seemingly unsolvable crime has captivated everyone from a pipe-smoking detective on 221B Baker Street to children clustered over Clue games in living rooms everywhere.
Mystery fiction, too, has captured its share of interest over the last 200 years, and the stage has hosted who-knows-how-many whodunits as well.
The latest comes from Dublin's Gate Theatre, which makes its ninth appearance at the Spoleto Festival with a new adaptation of Daphne du Maurier's 1951 novel, "My Cousin Rachel." The mystery-romance follows Philip Ashley as he deals with the death of his guardian. He comes to suspect his guardian's widow, Rachel, of foul play even as he falls in love with her.
The Gate has its work cut out for it, according to Otto Penzler, a mystery editor and proprietor of The Mysterious Bookshop in New York City. "Mystery novels and stories are cerebral," he said. "Most of what happens happens internally, in someone's brain. It's hard to show cerebral activity on the screen or the stage."
"My Cousin Rachel," the book, is told from Philip's perspective, and so the events and evidence are colored with his thoughts. But the stage lets other characters, notably Rachel, open up and capture the sympathy of the audience.
Hannah Yelland, the actress playing Rachel, sounded pleased about her ability to flesh out Rachel beyond Philip's singular perspective.
"One moment, you might be on her side and feel for her, she's lost her husband and is destitute," Yelland said. "Another moment and you have to wonder if she's a gold-digger. And you never quite know."
Toby Frow, the director, said he's looking forward to hearing what patrons think about the portrayals.
"I hope the audience is left torn about their feelings towards its two main protagonists, Philip and Rachel. They are each wonderful creations, full of contradiction and complexity," Frow said.
Despite the challenges the directors and cast face when adapting for the stage, the upside is clear. Agatha Christie's murder mystery "The Mousetrap" opened in London in 1952 and has been playing ever since; it recently celebrated its 25,000 performance in 2012. Among its successors are "Deathtrap," "Sleuth" and the second-longest-running non-musical play in London, "The Woman in Black," which has been continuously performed since 1989.
William Gillette, an actor and playwright in the late 19th and early 20th century, brought seven different Sherlock Holmes plays to Broadway, portraying the character more than 1,300 times over 30 years. (He was hardly alone: Holmes holds the Guinness World Record for the most portrayed literary human character, having been depicted on screen 254 times and played by more than 75 actors.)
The exact reason for the foothold that the mystery genre continues to have remains open to interpretation.
"It's almost a game between the audience and the performers," Yelland said, "that kind of need to figure things out, almost as though they'll get ahead of the characters and solve the mystery."
Frow said the form allows audiences to explore larger themes vicariously. "The mystery novel/film/play allows us to engage in huge dilemmas, but on a manageable scale," he said. "And of course without risking our own death at the end of the evening."
Nicholas Schmiedicker is a Goldring Arts Journalist from Syracuse University.