This isn’t the play I expected it to be, from the cutesy Friends-inspired title and the hint of romance in the storyline. I should have read the blurb more carefully: they bill it as “dark and uncompromising”, and they’re certainly not wrong. I won’t give away exactly what happens, but I can safely reveal that the story takes a startling turn - and that we’re soon in for a disquieting tale of possessiveness and false-heartedness, set against a backdrop of escalating tragedy.

James Fritz’s script debuted in Edinburgh in 2015, and in this Brightonian production, it’s Joanna Rosenfeld who’s alone on the stage. Playing both the male and female protagonists - neither of whom is ever named - Rosenfeld voices not just what they actually say, but also the unutterable thoughts inside their heads.

The couple’s friends think they were “meant to be together”, but in the privacy of her own mind the woman’s not so sure. She daydreams of a future with a different man - and chafes against the way she’s now permanently packaged with her husband, her name always mentioned as an adjunct to his. He, meanwhile, grows increasingly possessive; not in the sense that he imagines that she’s seeing someone else, but in the sense that he can’t imagine her having a life without him. As we listen in on these diverging trains of thought, the tension ratchets towards a conclusion that’s profoundly disturbing… yet logical and believable too.

Completely intentionally, Rosenfeld plays the two characters with very similar voices - and near the start, before I’d tuned in to the subtle differences she employs, she got halfway through some important scenes before I figured out whether we were listening to husband or wife. I’m reliably informed that the playscript doesn’t explain who’s speaking either, so that even the actor and director have to work it out for themselves. It’s the oddest of gambits and I admit it frustrated me at first, but over time I came to see the point: it keys into the theme of becoming a couple, of losing part of your own identity as two become one.

Each of the characters has their own defining scene, and it’s in the nuance of these moments that Rosenfeld truly excels. On the wife’s side, we witness a quiet breakdown, as the pressure of the situation overcomes her; not because of its direct impact, but because of the role society suddenly expects her to play. As the husband, speaking to an unseen bartender, she mercilessly explodes any hint of sympathy we might have had for his misfortune - capturing an unthinking, boorish malevolence which hides just below the surface of his apparent admiration of his wife.

If we’re honest about it though, neither of the characters is particularly likeable; the woman’s a touch too impatient for the relationship to end, regardless of circumstances, and the man’s far too anxious to cling onto his trophy wife. This is a complex story that tells complex truths - including the fact that inner thoughts can often be ugly ones. It’s a play that demands your full attention, but rewards it with both a thought-provoking script and a compelling performance. The final moments are haunting, and I found myself thinking about Ross and Rachel long after the lights had gone down.