We can’t resist the macabre allure of Nathan Leopold and Richard Loeb, the wealthy teenage lovers who killed a 14-year-old boy in 1924 for thrills, and who avoided the death penalty thanks to the humanitarian brilliance of lawyer Clarence Darrow (they received life sentences plus 99 years instead). Patrick Hamilton, Alfred Hitchcock and the novelist Meyer Levin are among those who, over the decades, have been drawn to their story, and in 2005 this bijou one-act musical by Stephen Dolginoff premiered off Broadway, focusing exclusively on the psychosexual dynamic between this bleakly twisted pair who believed themselves superior beings in the manner of Nietzsche’s superman.

Matthew Parker’s queasily intimate revival was first seen at Islington’s tiny Hope Theatre in 2019, and it’s a typically bold move by the scarcely more capacious Jermyn Street to transfer it: even the most seasoned theatre-goer will blanch at the scene in which Loeb, dapper in creamy three piece suit, airily discusses snatching a boy from a playground.

It’s Bart Lambert’s considerably less suave Leopold who tells the story of the pair’s journey from petty crims to infamous murderers, though, in the retrospective form of an explanation some 34 years later to a parole board (Loeb had been killed by an inmate many years previously). And what grips is not just the revolting nature of the pair’s murderously erotic compulsions, but the highwire pairing with Dolginoff’s eerily beautiful score, played by Benjamin McQuigg on a piano in the corner as though what we are watching is an old fashioned romance rather than a horror story.

That said, Parker’s production is a noirish nightmare, wreathed in furtive shadows and tinted light, and set in a dilapidated gumshoe office peppered with crime-scene photographs and press cuttings, as befits a story that remains an object of forensic fascination. As the apparently weaker partner, Lambert’s Leopold resembles a man child whose internal wiring appears to have gone awry, his body riven with nervous tics, his tongue compulsively touching his lips and finger tips, his demeanour by turns hideous and pathetic.

His sickly infatuation with the cooler, blither Loeb belies a relationship that is presented as transactional – the pair sign a contract in blood, with Leopold granted sexual favours in return for helping Loeb seek ever greater criminal thrills – yet Dolginoff implies nothing is what it seems in this gothic Faustian pact, with its multiple toxic shades of fantasy, cruelty and obsession.