And since this is a McDonagh play, things will become — untidy. You won’t know whether to laugh or hang your own head, in shame.

McDonagh, whose relationship with Phoebe Waller-Bridge — the actress and creator of “Fleabag” — has made the spotlight all the more glaring, was gracious and good-humored in acknowledging his distaste for interviews. But he answered every question posed, his lanky frame bent slightly forward, his responses serious one moment, comically provocative the next. (A 6-year-old coming at you with a knife would be asking for it, wouldn’t he? “It might be a butter knife,” he said. “But it’s still a knife.”)

He and his older brother, the screenwriter and director John Michael McDonagh, grew up in south London, the children of working-class Irish immigrants from counties Sligo and Galway. Their parents returned to Ireland in 1992, when the brothers were in their early 20s, leaving the family’s London home to become a two-man frat house for writing.

McDonagh’s struggle to find his voice ended when he stopped blocking out the Irish clatter in his head. “Once I did that, I think it freed something, in that it allowed me to write how I thought my uncles spoke — without it seeming like a rip-off of Pinter or Mamet,” he said.

This allowed him to play with Irish idiom, he said. “To kind of corrupt it slightly, but also to be truthful to aspects of it as much as possible.”

His first play, a success called “The Beauty Queen of Leenane,” was followed by several others also set in the west of Ireland. His dark-humored themes and settings have broadened since then, as evidenced by the three feature films he has written and directed: “In Bruges,” “Seven Psychopaths” and “Three Billboards Outside Ebbing, Missouri,” which won two of the seven Academy Awards for which it was nominated in 2017.