“Stakes are high,” observed Riley Berris, the theater teacher at San Marcos High School who is directing the school’s upcoming production of Agatha Christie’s murder mystery And Then There Were None. They certainly are, as none of the 10 characters who stay on the show’s island get out alive. It’s a game of survivor that nobody wins.

How appropriate for this Halloween season, but why do a murder mystery now at San Marcos? Berris explained: “In the last three fall seasons I’ve done a modern comedy, Steve Martin’s Picasso at the Lapin Agile; a serious drama, Moisés Kaufman’s The Laramie Project; and a classic comedy, George S. Kaufman and Moss Hart’s You Can’t Take It with You. This year I wanted to get away from the feeling of going back and forth from comedy to drama, so I decided to take on a murder mystery, which I think really is a different genre.” The choice of Christie’s story was made easier by the availability of Kevin Elyot’s fresh (2005) adaptation, a 21st-century version that nevertheless respects the period in which the original was written, and by a certain affection that Berris brings to the piece from her own childhood. “My brother and I read this together when we were young, and we loved trying to solve the mystery,” she said.

Sitting in the beautiful San Marcos theater during rehearsal, I can see how Berris has taken to her new home. She can do so many things at once from her position by the soundboard — spot things happening in the run-through taking place onstage and call for adjustments, use her stage-trained voice to gather and instruct other students from all over the room, and then turn to me and continue making insightful remarks about the play. “The end has shock value,” she said, “and the female lead has to deal with some serious issues, but overall my favorite thing about the piece is that there’s so little exposition.” Since the majority of the characters don’t know each other before being summoned, there’s no need for elaborate setups. What they do all have in common is a similar backstory — someone believes that each of them has at some point committed a murder.

The San Marcos theater students have gotten lots of unexpected benefits out of this programming decision. The cast got together for a mystery dinner party that Berris said was a lot of fun, and helped them focus on the play’s central question, which is, “Who can be trusted?” For a group of sophomores who are studying theater but are not part of the cast, the play has become the basis for an original composition. They are collaborating on a parody version of And Then There Were None that will be acted by the same cast as the regular play in the week following the run. It’s an example of the kind of innovative writing assignment that turns students into lifelong scholars and devotees of the arts.

For those who venture out to see the show, you can expect great acting from a dedicated — and in many cases experienced — cast, and you can expect to be held in an evening’s worth of truly uncanny suspense. The solution to this one is, unless you happen to have read or seen it already, fiendishly hard to guess. Good luck finding all the clues, and watch your back — there are murderers among us.

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And Then There Were None plays at the San Marcos High School Theater Thursday, November 2-Saturday, November 4, 7 p.m., and Sunday, November 5, 2 p.m. For tickets, visit shopsmroyals.org or purchase at the door.