I’d hoped to ease into the 2018-2019 theatre season, but Cyprus Avenue had other plans. True, the Public advertised it as a black comedy–but there’s black, and there’s the black of three a.m., when everything’s uneasy and fear seeps into the bones. We’re not five minutes in when the n- and c-words are launched in the direction of a black psychiatric case worker by her patient. He’s testing her, and the playwright, David Ireland, will test us for the next 100 minutes.

Crude language is the least of Eric’s sins. We know from the outset that Eric, an Irish Protestant Unionist, has done some nasty things, and flashbacks take us to the beginning of his woeful tale, when he calls his daughter a “whore” after refusing to bond with his granddaughter. The problem is that to his eyes the baby looks uncomfortably like former Sinn Fein leader Gerry Adams. In a time of peace, Eric is a man at war, with his past and himself, and his family provides ample collateral damage. As he drifts deeper and deeper into his Irish troubles, he convinces himself that the infant is Gerry Adams, and with a black marker colors eyeglasses and a beard onto her face. (The doll used gets a real workout here.) That’s enough for his wife and daughter to shun him, but more drastic measures are called for. Fortuitously mistaken for a “Fenian” by a Protestant hit man with scores to settle among the Irish, Eric convinces the stranger to fulfill his task by killing the baby instead.

Like I said, black. There is humor, notably Eric’s disdainful, and wonky, listing of Irish-bred cultural heroes (Barack Obama somehow rates), his plucking at the low-hanging fruit of Riverdance and Conan O’Brien, and jaundiced reading of the films of Ron Howard, including the sentimental immigrant Western Far and Away. But when the monologues give way to bloody mayhem, the show loses its grip as surely as its protagonist does. Fortunately, the splintered shards of Cyprus Avenue (from the Van Morrison song) are held together by its star. How to make a poor psychotic bastard like Eric appealing? Simple: Get the great Stephen Rea to play him. He’s a wonderfully seductive maniac, drawing us into his confidence, spitting us out when he goes too far, and swallowing us all over again.

But Rea can only get so far. The show, a critique of tribalism that fits right into the present moment here across the pond, gets more heavy-handed as it progresses (this is one of those 100-minute shows where every minute seems to weigh more and more) and the big shocks exacerbate a certain thinness to the titillating writing. (Ireland is no Martin McDonagh when it comes to plotting and execution, the last meant literally.) Vicky Featherstone’s direction on a barebones thrust stage, pushing Eric at us at all times, brings us closer to his menace. But neither she nor Rea can make the dire doings at Cyprus Avenue any more explicable.