We are in a fully-stocked, under-populated bar with a couple of men, one regular, one visiting, both haunted by the past with stories to tell.

No it's not Conor McPherson's The Weir, but Owen McCafferty's Quietly, set in Belfast, where Patrick O'Kane's brooding, bitter Jimmy is nursing a pint and waiting for the man, his nemesis and contemporary, who threw a bomb into this same bar thirty-six years ago – in 1974, when they were both sixteen – and killed his father.

Jimmy Fay's production for the Abbey in Dublin is, as the title implies, an exercise in emotional diffusion, a ground-level study of the peace process in action as Catholic Jimmy and Declan Conlon's circumspect Protestant, do their ironic bit for "truth and reconciliation."

Their circling, matador-ish contest, full of surprises, not least about their family backgrounds and social conditioning, is officially witnessed, as it were, by a Polish barman (Robert Zawadzki) who has his own experience of cultural dislocation.

Brilliantly, the play sidles into questions of national, as well as cultural, identity, the meeting timed to coincide with a football match on the television (being played in nearby Windsor Park), a World Cup qualifier between Poland and Northern Ireland; there was a match, too, on the day of the bomb.

The play may hinge on a handshake, but McCafferty's point is that scars never heal, tribalism runs deep, hate can be modified, dealt with, but remains. The intensity of the performances of O'Kane and Conlon contains seeds of hope and fear, and provides the most riveting encounter of my festival so far.

Quietly runs at the Traverse until 25 August