The tale is told by psychiatrist Peter Cleave from inside a top-security mental hospital in the late 1950s. (Closely modelled on Broadmoor, where McGrath grew up, his father being Super-intendent.) Cleave has studied the "catastrophic love affair charac-terised by sexual obsession" between Stella Raphael and Edgar Stark. (Check how pregnant with meaning even the names are.) A torrid, desperate, bleak love doomed by Stella’s marriage to psych-iatrist Max Raphael. Edgar, his patient, is interned for the murder and mutilation of his own wife. A sculptor, he worked the disembodied head on his armature: "For him the making of art and the maintenance of sanity had a precise and delicate relationship." The two meet when Stark is detailed to the doctor’s garden. They make love furtively, Stella reawakening from her moribund marriage, isolated from the exuberant life after which she hankers. Then her paramour steals Max’s clothes and absconds, leaving her torn between covering her own part in the psychopath’s flight, her anger at being used, and a conviction that such an animalistic lover would never abandon her to the atrophy of Max and their ten-year-old, Charlie. "You don’t control love," she says. He doesn’t forget, and soon Stella herself flees to join Edgar in his bohemian garret in an old Southwark warehouse. But when old jealousies reemerge, the artist’s violent nature begins to reassert itself.

McGrath has spoken of his work never visiting contemporary Britain. His books remain rooted in the slightly unreal world of the forties and fifties. Asylum is his most modernistic, but it retains the uncomfortable ambience of being set not only forty years ago but in the monolithic hospital and its omnipresent walls, under the grey shadow of Victorianism. This collision advances the book its tension.

Reading it, we’re brought up sharp on occasion, wondering at McGrath’s slightly eccentric narration - Cleave reports to us what he knows, when he was present, but also details the affair with nuances he could not possibly have witnessed, even second-hand through Stella. The result is a novel that switches between I and they - between first and third person - in a manner that at first seems foolish but gradually seduces with its accumulating eeriness. We are some way in before we realise that Peter Cleave is an unreliable narrator to lead us through such a very intimate darkness.

Asylum is rich in melancholy, beautifully sustained, engaging us passionately even while its art is cool, almost detached. And better yet, it joins that very select few (with Carroll’s Sleeping In Flame another) that retain - even bolster - their mysteries in (and beyond?) the very last line. Sublime.