In the high stone tower of an isolated naval fortress, Alice and Edgar are about to celebrate 25 years of wedded bliss—if decades of resentment, recrimination and mutual sabotage count as bliss. But when an alluring visitor arrives, the delicate balance of their tedious arrangement falls off its axis, cracks growing into canyons. In Conor McPherson’s wicked take on Strindberg’s masterclass in marital warfare, a twisted love triangle waltzes off the edge of a cliff, plunging us all into the deep.