With immigrants across the USA bracing for planned Ice raids this weekend, Lunatic 19’s, a topical new play by Iowa-based writer Tegan McLeod, shines a spotlight on the soullessness and absurdity of American immigration laws and procedures. A tense two-hander, it’s the kind of story you want to dismiss out of hand as an exaggerated, politicised version of the truth – but only because accepting that this sort of thing can and does really happen is an idea too horrific to contemplate.

Gracie Reyes (Gabriela García) is an undocumented migrant worker, who’s originally from Mexico but has called Kentucky home since she was a child. After narrowly surviving a horrific car accident, she’s taken from her hospital bed, neck brace and all, handcuffed and bundled into a windowless van for the long drive back “from whence she came”. Her driver and captor is Alec (Devon Anderson), whose career depends on getting Gracie back to Mexico promptly – but as the days pass, it becomes more and more difficult for him to view her as just another number. And so what we end up with is a dark take on the traditional road trip buddy movie, in which it seems increasingly unlikely that there can ever be a happy ending for either of them.

Framed as a nightmarish, almost dystopian, memory playing out on a minimalist set (Carla Goodman), the play is outstandingly performed – both as individuals and as a partnership – by Gabriela García and Devon Anderson. García is enthralling to watch as Gracie, a survivor who’s lived through more trauma than most of us can even imagine. Though she approaches most conversations with either stoic resignation or bitter sarcasm (which only warms the audience to her even further), underneath it all she’s clearly terrified and confused by the indignity of her situation and the prospect of being dumped without warning back in a country she barely remembers.

Similarly complex is Devon Anderson’s Alec Herrero, who may not be facing deportation but is, in some ways, just as desperate. Also of Latino heritage, he sees all too clearly in the “cargo” he transports how his own life could have been very different – but with a wife, three daughters and a troubled sister to support, he needs this job. Little by little Anderson’s facade of emotionless authority slips to reveal a decent, caring human being who’s trapped by his own circumstances into becoming part of a system he knows is wrong. And although his developing relationship with Gracie has a certain inevitability to it – this is a road trip story after all – their chemistry never feels forced.

A particularly effective aspect of Jonathan Martin’s production is the sparing but frequent use of blood as both a physical prop and a metaphor. Gracie’s body – and her blood in particular – has betrayed her many times; she’s a haemophiliac with a history of multiple miscarriages, who had the misfortune to be born in the wrong country. So while many parts of her story are portrayed figuratively rather than literally (there’s no van, no pharmacy, no detention centre, not even an actual road), it feels appropriate that the blood at the heart of the story is all too real.

Despite some very funny lines of dialogue, there’s nothing particularly humorous about Lunatic 19’s – especially when you only have to turn on the news to understand that stories like this one are not just true, but also completely legal. The utter absurdity and inhumanity of a system that values the worth of a human being purely by where they were born makes for difficult viewing, but the story is so well told that the time we spend with Gracie and Alec – though frequently harrowing – feels considerably shorter than its run time of 90 minutes. An excellent production, and essential viewing.

Lunatic 19’s is at the Finborough Theatre until 3rd August.