A Slight Ache is one of Harold Pinter’s lesser-known works… which is often followed by the rejoinder ‘And for good reason!’

However this Fringe revival offers enthralling, intense and ambiguous performances by its two leads, comedians Thom Tuck and Catriona Knox, portraying a well-to-do, middle-class, later-middle age couple facing up to repressed anxieties that threaten their cosy existence.

The conduit for this is the elderly match-seller who has mysteriously appeared on their road, crashing into their utopia, a blossoming garden on a summer’s day. Mute and unemotive, he is a blank canvass, both characters projecting their particular fears on to him. For Edward, it’s ageing and illness – the worry that the ‘slight ache’ in his eye is symptomatic of greater decay. For Flora, it’s repressed sexual feelings and perhaps a life she could have had

It’s never quite certain if the match-seller, played by a sinister, inscrutable, Simon Munnery, really exists or is merely a cipher. It transpires the play was originally written in 1958 for radio (thanks, Wikipedia), which would put the answer to that question entirely in the mind of the listener. Here we have to semi-overlook the fact he’s standing right in front of us, albeit largely hidden by a balaclava.

Tuck captures the essence of a disinterested husband and pompous oaf – ‘I’m not the squire but [the villagers] look on me with some regard’, his character, an academic, intones. But he becomes angrier and finally weaker with the stranger’s presence. Knox is the dutiful wife, but under the influence becomes mesmerisingly enigmatic, shifting from restrained lust to anger to compassion.

Simply but effectively staged here, the play has lines that crackle like the single fluorescent light strip-cum-bug-zapper on the stage, which the actors fill with unsaid meaning. The climax, though inevitable, is a little disappointing, but there’s plenty of tension and compelling characterisation along the way.