Give Me Your Love (Battersea Arts Centre)

The title sounds soft but the drugs are hard. Whereas once you altered your mind, or expanded it, or at least thought that you did, when you took off on a trip, man, nowadays "illegal substances" are increasingly validated as medical treatment.

And in this show, this means the experience of serving soldiers suffering from post-traumatic stress disorders: Zach, in this second leg of a trilogy from David Woods and Jon Haynes of Ridiculusmus, is a Welsh squaddie who lives in a box and craves ecstasy.

This ecstasy, a tablet of MDMA (an acronym for a compound word as long as that song title in Mary Poppins), is dangled tantalisingly outside his grimy living space by his best friend and psychiatrist, or one of them. Zach is in retreat, and limbo, after serving in Iraq. But increasingly it becomes clear that, although he tells his offstage wife that he went to Iraq because he loved her, Zach is in trouble generally, and at odds with the world, deeply unstable.

The account of some terrible incident he witnessed may or may not be reliable. Instead of a medical report, we have an imaginative breakdown of, well, a breakdown. Beckett did this with Winnie in her mound of earth, a life in hard shards and fragments; but with Zach in his box, the detail is unconvincing, partly because it's meant to be – he's an unreliable witness of his own experience.

This creates a problem, dramatically, because the imagery of the stage is so strong, you want everything that is said to be true. The writing doesn't fizz with the moral anger and psychotic valour of a play like Heathcote Williams's AC/DC (a play about drugs from the other end of the recreational spectrum), nor does it constitute a poetry of despair as in Beckett.

But it is quite funny, in a gloomy sort of way, and David Woods's Zach is a tragic version of the bed-bound Oblomov in his upside down cardboard home, visible only by his calves and trainers. Body parts only, too, for Haynes, who whispers offstage as the impatient wife, Carol, and reveals the odd limb round the scenery as Zach's best mate, stooge, supplier and sounding board.

In the first of this trilogy, The Eradication of Schizophrenia in Western Lapland – there's a title to get you rushing to the box office – critics welcomed a more light-hearted take on mental illness in the home. This show strikes me as a plea for drug treatment as a cure-all, and not just for soldiers. Where next, I wonder? Drugs and cardboard boxes for the homeless? Not too bad an idea, perhaps, and Zach is half-way qualified already.

Give Me Your Love runs at the Battersea Arts Centre until 30 January.