Imogen Poots and James Norton deliver a compelling portrayal of a dysfunctional relationship on the edge of a crisis. At first it’s very much within the bounds of normal twenty-something anxiety, self-medicating with booze and drugs and messy student living. But the mess soon threatens to subsume them both as their minds and lives unravel.

American newly-weds, Zack and Abby are the first of their friends to get married and we find them holed up in a chaotic rental flat in bohemian Quartier, Belleville, Paris. Abby is coming of medication for anxiety triggered by her mother’s death a few years before. She’s completely wired, just back from teaching a yoga class where no one turned up and Zack has thrown a sicky from his AIDS research post.

Poots sustains Abby’s anxious and paranoid state effortlessly, she’s often very funny which is good news for us as this is where Herzog’s dialogue shines. Her rants are half clever, half funny, half desperately sad as she over-thinks, second guesses, bullies, pleads and finally collapses on the sofa. For much of the play Norton's Zack seems like the saintly partner, desperate to make his clever, volatile wife happy. Endlessly forgiving and kind. It gradually becomes clear that he has in fact completely lost hold of his own life and is just about clinging on.

What Herzog’s play does brilliantly is explore the sickness within apparently ordinary relationships and the way this particular generation try to prop themselves up. Director Michael Longhurst holds on to the sense of ‘normal’ for as long as possible, with a rumbling threat of catastrophe slowly drawing nearer. There are many new plays about mental health ‘issues’ written at the moment but few so subtle as this.

The least effective element of the play is the Senegalese born French land-lords who live below. Alioune and Amina played by Malachi Kirby and Faiht Alabi speak french for much of the play and seem to have a largely symbolic role, showing what a functioning couple are doing at the same stage in life. They are watchful and reasonable, cleaning up the ‘mess’ the Americans leave behind. But in comparison to the richly drawn naturalism of Zack and Abby their symbolic roles often felt stilted and a little odd.

What Longhurst’s production does to perfection is examine the savage and symbiotic nature of young relationships. Funny, familiar and at times deeply uncomfortable, it’s is a thrilling walk along the fine line between OK and out of control.