St. Helena Drama’s “The Play That Goes Wrong” opens Thursday

Expect missed clues, faulty lines, faulty props, faulty sets, lighting and sound errors, and terrible acting (why is that corpse moving so much?).

That’s all intentional, though, because “The Play That Goes Wrong” is a comedy about an inept English theater company that stages – or at least tries to stage – an old-fashioned stage mystery called “The Murder at Haversham Manor.”

The cast and crew say that while there is room for improvisation, the fictional Cornley Polytechnic Drama Society’s hilarious flaws are the result of careful scheduling and months of St. Helena Drama rehearsals.

“Everything has to go right so nothing goes wrong,” said actor Hartleigh Demchuk.

This is not a backstage comedy. In a meta twist, audiences at the St. Helena Performing Arts Center will see an actual performance of “The Murder at Haversham Manor” where Murphy’s Law reigns supreme.

You’ve probably seen mistakes in a live performance, but have you ever seen the lead actress (Sonny Calder) accidentally fall unconscious? Or does a dog get lost and the actor playing its owner (Xander Kelperis) walks around on a leash pretending the dog is still there?

Alexis Lund directs sound engineering and is responsible for the show’s sound effects and nine microphones, one for each lead actor. She works closely with stage manager and lightboard operator Charlotte Hoffmeister, who helps turn the microphones on and off at the right times so you don’t hear backstage chatter.

And if so, how do you know that this isn’t one of the series’ many intentional mistakes? During a 20-minute preview last week, it emerged that what appeared to be errors from the St. Helena Drama cast and crew were part of the show.

At least most of them were intentional – director Patti Coyle said after the preview that a piece of scenery that fell to the ground wasn’t meant to do so until a later scene. In any case, it was fun.

Some of the comedy revolves around prop errors. Part of Hoffmeister’s job is to ensure that these props are in the right (or wrong) place at the right (or wrong) time. If not, “entire jokes written into the script don’t make sense,” she said.

When Calder first read the script, she thought it would be easy, but she said it was the most difficult non-musical she had done in her four years at St. Helena Drama – much more difficult than “She Kills Monsters.” from last fall.

“The plot is quite complicated, everything has to be placed carefully and the timing is really difficult,” she said.

Josie Doda, who also starred in “She Kills Monsters,” agreed.

“There are so many moving parts,” she said. The fight scenes in “She Kills Monsters” were like a “choreographed dance,” she said, but the humor in “The Play That Goes Wrong” was more unpredictable. If something goes legitimately wrong, the cast needs to make it seem like it’s part of the show.

“The improvisations we did in class are really useful,” Doda said.

“The key is timing,” said Leo Fitzpatrick. “The jokes don’t work if you’re wrong for just a second. We have a scene where we’re interrupted, and if the interruption comes too late, the joke loses momentum.”

The set also offers challenges. Unlike other St. Helena Drama shows, the set is completely opaque, meaning the cast and crew backstage cannot see what is happening on stage. There are other problems with the set that would be a shame to spoil.

Not that “The Play That Goes Wrong” is a purely technical exercise. Peter Oliver, who plays the lead, says this is the funniest show he has ever done with St Helena Drama. And even cast members who don’t have lines, like Tilly Dodd, say the show gives everyone a chance to laugh a little.

“It’s a lot funnier than anything else we’ve ever done,” Rosemary Vasquez said.

The Play That Goes Wrong is directed by Coyle and based on the British production (later exported to Broadway) written by Henry Lewis, Jonathan Sayer and Henry Shields.

The show runs this weekend only (October 17-20) at the St. Helena Performing Arts Center, 1401 Grayson Ave. Tickets are available at sthelenadrama.com.