Our Boys starts with a montage: the kind of montage you'll see in many a military-themed show. A group of men salute, march, shoulder arms in unison; it's an impressive display of precision and soldierly technique. But then, just seconds into the action, the order devolves into chaos. A bomb has gone off in Afghanistan – and for these young men, the war is over.

When we next see the group of soldiers, they're in the military wing of an unnamed hospital, slowly recovering from both physical and mental wounds. Ian, the most obviously damaged of the contingent, can speak only with effort and needs assistance to get to the toilet; Joe's injuries are minor in comparison, but perhaps he's been wounded in a way we can't see. Into this pre-formed group comes a young Potential Officer, yet to make his way to Sandhurst, admitted not for a battle injury but for an embarrassing problem with his bowels. The rules say the men should call him "sir", but they have their own hierarchy and their own evident leader… and in some cases, their own reasons to distrust those with authority to command.

The set-up isn't entirely without stereotype – the squaddies in the main are coarse and ignorant, while the Potential Officer is nice but dim – but as we get to know them better, those initial impressions drop away and rounded characters are formed in their place. The awkwardness of the situation is well-portrayed, and there's plenty of humour in the all-male group's often crude banter. They do it for a reason, we sense: both to build camaraderie, and to open the door to talking about things that otherwise are too uncomfortable to confront. For me, the most unexpectedly touching scene comes when the badly-injured Ian is forced to reveal a highly personal problem. One by one, the other men admit that it had happened to them too, and reassure Ian that it won't last forever.

The comic highlight comes in a messy game of "Beer Hunter", a parody of Russian Roulette involving shaken-up cans of larger. And that scene is the trigger for a different kind of game: a serious one this time, a high-stakes power-play filled with bluff and deception, where the full weight of military discipline is brought to bear and the newfound friends' entire futures are on the line. I'm not convinced this part of the plot is entirely realistic, but it fits the great tradition of stories about wily soldiers getting one over on their superiors, and it opens the way to a tense and credible conflict which looks set to drive the now tight-knit group apart.

On several occasions, I rolled my eyes at startling events which at the time seemed overblown; the shock finale, in particular, hovers on a delicate line between visceral and laughable. But here's the thing. To make sense of some of what's happening, you have to know an essential piece of back-story – a crucial motivation for a central character – and that key information is only revealed in the last few scenes. If we'd been let into the secret a little earlier on, then that dramatic conclusion would seem more believable, or at least a little easier to understand.

It feels like playwright Jonathan Lewis is telling the story backwards; but on the other hand, I think that's kind-of the point. We're peering into a pressure cooker – a boiling mess of remembered traumas and suppressed frustrations – and we can't demand a neat dramatic order from the things that bubble to the top. We learn about the consequences of war on those who fight it, and some of what we witness is scary and difficult to understand. But there's a reason for that, as the script advises us: it's because, while you can look at physical injuries, "you don't see what's inside".