Infidelity may ruin marriages, but it is a fascinating subject for plays.

“It can make for really comic theater, but it can make for a really squirmy, uncomfortable kind of theater,” says Rob Cope, who is directing “Private Eyes” by Steven Dietz at Salem Theatre Company, which opens this Saturday, April 23. “Some of my favorite plays end up having to do with infidelity and affairs.”

Cope had been looking for a work to stage — his first as a director — when a colleague suggested “Private Eyes,” which was first produced in 1996.

The first act introduces the audience to an actress, Lisa, who is auditioning for another actor, Matthew.

“Suddenly that reality is broken, and then you realize, ‘Oh, I’ve been watching the rehearsal of a play,’” Cope says. “That first scene, the play within the play, is an audition for a play, and the characters reference the play within the play repeatedly throughout.”

If that sounds complicated, it gets even more complicated when new characters are introduced.

“One of the characters visits a therapist, but when the character visits the therapist it begs the question: is this therapist real?” Cope says.

These shifts in reality create a sense of distrust in the audience about what is true, just like someone who wonders if they are being cheated on by a partner.

But the play also shows that feelings of suspicion are often denied by people who are being betrayed, because they can’t accept what is happening.

“When we’re confronted with things we don’t want to believe are true, we put up this separate reality, to try to deflect the reality that we see, that’s clearly there in front of us,” Cope says. 

While the events in the first act may be jarring, the second act reviews them in a way that helps explain the story, while bringing larger themes into focus.

“By the time you get to the end of the first act, you’ve been in that water for about 30 pages,” Cope says. “Then we start digging deeper into the story itself.”

Cope’s interest in plays about affairs stems partly from his affection for Woody Allen’s films, where infidelity is a common theme, but he also has personal experience with the subject.

“I grew up around it,” he says. “It was something I learned about at a young age — that people do this.”

Not only did his parents separate after an affair, but Cope was also betrayed by a fiancee.

“Even if you’ve never had an affair, or been the victim of an affair, it’s the horror story of marriage,” he says. “Nobody wants to be on the cheated-on side.”

Cope, originally from St. Louis, earned a Master of Fine Arts in 2014 from the University of Florida School of Theatre and Dance.

He originally studied film in the 1990s, but walked away from “the world of acting in film and theater,” and worked in the hotel industry for 10 years before returning to school.

“I thought I would take a look back at the thing I loved,” Cope says.

When his wife’s work brought them to the Boston area, he started auditioning for acting roles “left and right,” and landed a role at Salem Theatre Company in “Crime and Punishment,” which was staged in early 2015. 

Cope also worked as a fight choreographer on several productions, applying skills in unarmed combat and rapier and dagger fighting that he learned in graduate school.

“When I was doing ‘Crime and Punishment,’ there was a scene in the play where Raskolnikov kills the sisters,” he says. “The way it was written in the play, the two sisters who are killed are played by one actress.”

That made their murder tricky to stage, but Cope suggested a solution to Catherine Bertrand, who is the artistic and managing director of Salem Theatre Company.

“She invited me back to do the choreography for a brief bit of violence in ‘Rocky Horror,’ then full fight choreography for ‘Hamlet,’” he says. “So Catherine and I have been building a relationship.” 

They discussed the idea that he might direct a play for the theater company, and agreed that “Private Eyes” would be a good place to start. 

“I spent the last three years or so paying attention to directing, and watching the things I think work and don’t work,” he says. “It’s something I’ve enjoyed doing in a smaller scale, and I thought it was time to throw my hat into the ring.”

If you go

What: “Private Eyes: A Comedy of Suspicion” by Steven Dietz

When: Saturday, April 23 to Saturday, May 7; Thursdays, Fridays and Saturdays at 7:30 p.m., and Sundays at 3 p.m.

Where: Salem Theatre Company, 35 Congress St., 3rd floor, Suite 301, Salem 

Information: Tickets, $12 to $28, at www.salemtheatre.com. Previews: Thursday, April 21 and Friday, April 22, tickets $20/$10. Opening Night and Reception: Saturday, April 23, cash bar available. LGBT Night: Friday, April 29, cash bar available. Student Night: Thursday, May 5, $5 student tickets.