Brendan Gleeson is an actor beloved by directors; he’s collaborated with the likes of Anthony Minghella and Martin Scorsese. But perhaps no filmmaker has served him better than John Michael McDonagh, who cast Gleeson as the lead in the dark comedy “The Guard,” which went on to become the most profitable film in Irish history. Now, Gleeson is earning some of the best reviews of a very heralded career for his new collaboration with McDonagh, “Calvary.”

In the film, Gleeson plays Father James, a priest who is taking confession from a mysterious parishioner. The confessor reveals that as a boy, he was repeatedly molested by a priest. To make the church pay, he is going to kill Father James in one week—because murdering a good priest will hurt the church more than if he killed a bad one. After debuting in limited release on Aug. 1 with an impressive per-screen average, “Calvary” will expand into nearly 40 more theaters this weekend.

Says McDonagh of his inspiration, “I was trying to do something that wasn’t’ going to be ‘The Guard 2.’ And I’d watched a lot of Bergman movies and thought, ‘They’re not making movies like that anymore, they’re not dealing with those kinds of subjects. I’ll do that.’ But I still wanted to give it a genre hook, that murder mystery element, just to bring the audience in who might be put off by these philosophical ideas.”

Says Gleeson with a laugh, “I feel doubly lucky to have snagged this role, given that his main priority was not to do ‘The Guard 2.’”

Gleeson met McDonagh after working with his younger brother, Martin McDonagh—first in the Oscar-winning short film “Six Shooter,” than in Martin’s feature debut, “In Bruges.” Asked how Gleeson became their go-to actor, McDonagh simply says, “If you’re friendly with a great actor, be pragmatic about it and use that great actor.”

Adds Gleeson, “Likewise, if you’re very friendly with a pair of great writers, what are you going to do?”

The idea for “Calvary” actually come up while the duo were working on “The Guard.” Recalls McDonagh, “The idea was a good man, a good priest, and what that would entail in a modern life where everything is ironic and insincere. Let’s follow a sincere man through to the end.” While Gleeson committed on the spot to the movie, he admits he “wasn’t quite prepared for the script that came.”

McDonagh, for his part, says he would never normally send a first draft of a script to an actor. “Because if they turn you down, what are you going to do?” But he also knew Gleeson would give him great notes. In fact, it was at the actor’s urging that McDonagh expanded upon the character of James’ daughter Fiona, played in the film by Kelly Reilly.

“I loved the Fiona character and missed her when she wasn’t’ there,” Gleeson notes. “Those were the scenes that really broke my heart and allowed me know the man behind the priest. And I said as much to John.”

As a result, McDonagh added some scenes with Fiona, including one where she gives confession to James. “She talks to him as a priest, but also as her father,” he says. “And when I look back at the movie now, I think those are some of the most moving scenes in the film.”

In addition to Gleeson and Reilly, the cast is full of great actors, including Aiden Gillan, Chris O’Dowd and M. Emmet Walsh. “I think it’s one of the greatest casts ever assembled for an Irish movie,” says McDonagh. Also in the cast is Gleeson’s son Domhnall Gleeson, who plays a psychotic killer that James visits in prison.

The elder Gleeson admits it was rough shooting such intense scenes with anyone, let alone his son. “They were tough,” he says. “We kind of didn’t really speak for days beforehand. We went into our separate corners and come out fighting.”

With two films set in Ireland under their belts, McDonagh promises there will be a third in the collaboration. He teases that in the next one, Gleeson will play “an abusive paraplegic who hates all able-bodied people, which means he basically hates the entirety of society.” The man is drawn into solving the murder of one of his disabled friends. Jokes McDonagh, “Brendan, as we speak, is researching the role by sitting.”

Quips Gleeson, “If you ever see my lounging around, I’m working on what I call ‘backstory.’”