The Irish are famous for wakes, parties and wakes that are also parties; but Frank McGuinness’s new play involves something rather different, a 21st birthday party that’s very much a wake. The performers onstage at the Almeida include Eileen Atkins as a batty yet sly old crone and Imelda Staunton as her cousin by marriage, a tough Donegal peasant turned domineering Dublin academic; but nobody’s presence is more strongly felt than the reason for this grim celebration, the suicide of a 19-year-old boy exactly two years ago.

Why do people kill themselves, leaving baffled, troubled relatives behind?

Specifically, why did Gene McKenna swallow litres of liquor and cut his wrists on the beach near his parents’ West-of-Ireland cottage? I don’t think I’m revealing too much if I say that the suicide note which appears just before the interval, whetting appetites for the second half, might be an ancient rune for all the light it sheds on Gene’s motives.

Was he into drugs and gambling? That’s possible, given that he was stealing from his mother. Was there something about the family, the culture or Ireland that plunged him into despair? Certainly McGuinness betrays more than a hint of cynicism about the Celtic Tiger. Gene’s father, Ian McElhinney’s Leo, has become filthy-rich through his chain of pubs. His wife, Staunton’s Margaret, has clearly hardened her already hard self to thrive at the university. The family isn’t happy — but how could it be, given that everyone is preoccupied, haunted, ravaged by this unexplained and maybe inexplicable death?

This is a dense, and, at times, a difficult play that raises plenty of pertinent and not-so-pertinent questions. But the main one is this: how do people cope with suicide? Through shallow, irrelevant quarrels, like Leo and Margaret? Through quiet, grieving colloquies with the dead, like McElhinney’s passive-seeming Leo? Through shows of anger and bossy aggression, like Staunton’s Margaret? But no strategy works, because loss is loss.

Aidan McArdle and Elaine Cassidy are on hand as Gene’s siblings but add little to the play’s arguments about death, self-slaughter and bereavement. As for Atkins, her contribution is interestingly inscrutable. She’s the family witch or, as she says, the “confused fairy” who found Gene on that beach and kept his suicide note from his parents. But why? To relieve her loneliness by privately possessing the boy’s last testament? Or just to add tension to a play that threatens to get bogged down in agonised elegy?

I don’t know; but I do know about the acting in Michael Attenborough’s production. You fully believe that Staunton’s Margaret, whose order is that “there will no weeping this weekend”, can bake Gene a posthumous birthday cake and, eventually, succumb to helpless, hideous screams of pain. And you will marvel at Atkins’s ability to rabbit crazily and comically on about everything from her love affair with Lucifer to Ireland’s lamentable lack of edible snakes, and yet, through her piercing eyes and intense gaze, to imply that she understands more than anybody. Top-notch performances, both of them.

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