Ma, Pa and the Little Mouths at Traverse Theatre. Photo: John Johnston

In what appears to be a high-rise flat in Glasgow – albeit one in which the curtains are taped shut and the curios and mementos of the characters’ lives are caked to the walls with a smear of deathly-white plaster – two repulsive yet strangely compelling characters hold court. Gerry Mulgrew’s Pa is browbeaten and lost in reverie, transported by the nostalgic smell of custard and the knowledge that he was once a beautiful blonde baby whose photograph caused admiring remarks from passers-by, as it stood in a Paisley shop window.

Karen Dunbar’s Ma, meanwhile, is a creature of scything sarcasm and belittlement, her obvious sometime-love for her companion buried amid a landslip of embitterment that has slowly encroached on the pair over the years. That Ma, grey and apparently elderly, is heavily pregnant is not the strangest element of this eighty-minute absurdist work from playwright Martin McCormick, directed by Andy Arnold for the Tron Theatre and the National Theatre of Scotland, and now playing at the Traverse theatre.

The air of stifling, claustrophobic routine the pair build is burst and then reconstituted as something far more sinister when it’s revealed that Nalini Chetty’s Neil has been showering in the next room, after accepting assistance from Pa when she ‘fell’ under a parked car down in the fearful world which exists on ground level. It’s never quite clear whether this is a dystopia, or just a bad neighbourhood in the present day.

Pa insists on washing her clothes, and as Neil walks around in just a towel, his codgerly inappropriateness grows (at one point he serenades the pair with a creaking Gary Glitter song) as Ma’s jealousy burns with ever-greater venom. “You look like someone’s cut a hole in your head and shone a torch through it,” says Pa, attempting a compliment of Neil’s bright smile, but it sounds like a grizzly threat. His assurance not to worry, that the front door is locked against whatever menace threatened her outside, is one which emphasises that she’s trapped.

It’s a piece which reminds immediately of the nearby Royal Lyceum’s Zinnie Harris-scripted version of Ionesco’s Rhinoceros which appeared during last year’s Edinburgh Festival, one which presents a patently nonsense scenario and manages to somehow wrest the least pleasant of emotions from it. Mulgrew is amiable and paternal; Dunbar is a fearsome comic actor in a particularly Glaswegian tradition; Chetty plays naïve and fragile, balancing the extremities of the others’ performances. Yet each steps outside the action to give their own powerful and horrifying monologue.

Pa’s in particular – on the nightmarish abduction and feasting on of his and Ma’s “little mouths” by an enormous serpent – is skin-crawling. Like the elusive snake, this is a play whose meaning and import is difficult to grasp, yet whose impact remains long after it has finished.

Ma, Pa and the Little Mouths was on until 19 May 2018 at the Traverse Theatre. Click here for more details.