Bill Cain keeps telling Oregon Shakespeare Festival actors that "Equivocation" is not complicated. The history-themed drama about the Gunpowder Plot of 1605, directed by OSF Artistic Director Bill Rauch, will have its world premiere at 8 p.m. Saturday, April 18, in the OSF's Angus Bowmer Theatre, 15 S. Pioneer St., Ashland.

Bill Cain keeps telling Oregon Shakespeare Festival actors that "Equivocation" is not complicated. The history-themed drama about the Gunpowder Plot of 1605, directed by OSF Artistic Director Bill Rauch, will have its world premiere at 8 p.m. Saturday, April 18, in the OSF's Angus Bowmer Theatre, 15 S. Pioneer St., Ashland.

History records the actual event, which inspired England's Guy Fawkes Night (each Nov. 5), as one in which dissident English Catholics plotted the destruction of Parliament and the death or overthrow of Protestant King James I. The extent of the conspiracy has long been a subject of debate, as has the exact role played by Robert Cecil, the king's chief minister, who has even been accused of complicity in the plot.

"It's a simple play," Cain says, tongue firmly in cheek. "It has five plays within the play, a drawing and quartering, a beheading and two hangings."

The play explores Shakespeare's (in the play the playwright is called Shagspeare or Shag, perhaps reflecting real life, in which the actor from Stratford did not style himself "Shakespeare") attempt to write a play that will please — or at least not offend — the king, and what it means to tell the truth or to lie, not only in politics but it art, and life.

The OSF is presenting the play as part of a thematic trio along with "Macbeth," which is running all season in the Bowmer, and "Henry VIII," which will open on the outdoor Elizabethan Stage June 12 and run through Oct. 9.

The connections are easily visible. "Henry VIII" chronicles the king's — and England's — break with Catholicism. "Equivocation" addresses the repercussions 100 years later. "Macbeth" is what the play's play-wihin-itself eventually becomes.

Cain and Rauch met years ago. Cain more recently developed "Equivocation" through the Ojai Playwrights Conference as part of the New Works Festival at TheatreWorks, in Palo Alto, Calif. It had a reading at Ojai in 2007.

Cain says a mutual friend gave Rauch a copy to read, and with that Cain found himself nervously second-guessing his decision to devote a chunk of his life to writing a play about something that happened far away 400 years ago and remains somewhat obscure to most people, and about which the whole truth will probably never be known.

"I spent three days thinking I'd written the wrong play," he says. "Then Bill called and said they'd like to do it in repertory. This is like a fairy tale."

In the play, it's 1606, and Cecil commissions Shag to write a drama about the previous year's events, adding that he should include dialogue complimentary to the king. And witches. The king is fascinated by witches.

Actors playing actors in Shag's company, the King's Men, play about 20 roles: conspirators, executioners, priests, jailers, court officials and characters in two unnamed plays that we now know as "King Lear" and "Macbeth." According to the OSF, the actors' verbal acuity adds a dark humor to leaven the potentially perilous task before them.

The cast has Anthony Heald as Shag, Richard Elmore as Richard, Jonathan Haugen as Nate, John Tufts as Sharpe, Gregory Linington as Armin and Christine Albright as Shag's daughter Judith.

Scenic designer Christopher Acebo has created a space said to be reminiscent of Shakespeare's Globe Theatre. It will also serve as court, prison and rehearsal stage. Costumes are by Resident Costume Designer Deborah M. Dryden. Lighting is by Christopher Akerlind, music and sound by Andre Pluess.

Cain is a Jesuit priest, a former teacher in a small, Catholic elementary school on the Lower East Side of Manhattan and a former artistic director of the Boston Shakespeare Company, where he says he directed most of the Canon. He is the author of "Standup Tragedy," a play about an idealistic teacher in a tough New York City Catholic school. The play won critical acclaim, but the Broadway production closed after 13 performances.

In 1997 Cain was a co-creator of the short-lived ABC television series, "Nothing Sacred," which outraged some Catholics due to the doubts of the central character, a priest, about his faith.

Cain says the germ of "Equivocation" appeared to him in the wake of the 911 attacks when he was in England.

"What came to me was the relationship of the Globe to the Tower," he says.

The historic structures stood near one another.

"The stories told by the prisoners were engraved on the walls in the Tower of London," Cain says. "I thought I'd like to write like somebody of conscience trying to leave one word behind."

In Cain's view, Shakespeare, who often wrote in support of the monarchy, made himself invisible in the Protestant-Catholic struggles, perhaps the day's central issue.

"He's the only writer whose very existence is a matter of debate," he says. "People of conviction were routinely being imprisoned, and Shakespeare did well for himself. He was writing in support of regimes that had extremely questionable stances."

Cain asks what in the end makes writing truly great.

"Is it a single word like those in the Tower? Or a body of 38 plays in which the author's view is largely invisible?"

"Equivocation" sounds like it's at least in part an answer to that question.