Two strangers walk into a bar. It sounds like the setup for a joke, but in The Weir, Conor McPherson’s 1997 play, it’s the start of an unsettling 90 minutes. Jack and Jim are regulars at a remote country pub in Ireland run by the young and quiet Brendan. They’re so familiar with the place that Jack helps himself to pints from behind the bar. One evening, their usual rhythm is interrupted by the arrival of Valerie, a newcomer from Dublin, brought in by the arrogant Finbar. In classic Irish fashion, the three men greet her with warmth and folkloric ghost stories. But when Valerie begins to share her own haunted tales, the playful atmosphere takes a darker turn. Ciarán O’Reilly directs the Irish Rep’s fourth production of the play since 2013. —Jeanne Malle