Last of the Boys (Southwark Playhouse)

It was smart of director John Haidar to think of writing to regional playhouses in the United States to find out what new plays over there might be in need of a European premiere. And if Steven Dietz's Last of the Boys isn't quite the overlooked masterpiece he perhaps hoped for, it is nevertheless a meaty meditation on the war in Vietnam which speaks pretty loudly about the dangers of military intervention today.

In fact, though Haidar sees it as relevant to Syria, Dietz's play was unveiled in 2005, at the height of the Iraq war, and is set in the last summer of the 20th century. Its theme, though, is Vietnam and the long shadows that disastrous "prolonged tactical exercise" has cast ever since.

Ben, a 50-something Vietnam vet is the last inhabitant of a Californian trailer park, symbolically abandoned by the other residents because it is polluted by toxic waste. His isolation is broken by the arrival of Jeeter, his former comrade in arms, and now a sometime-mystic truth seeker and a sometime lecturer at a small university, who spends his summers following the Rolling Stones on tour and holding up a sign begging them to stop.

On this occasion, however, he has just returned from Ben's father's funeral – which seems odd, since he has apparently only known him for three days, and odder still since Ben himself did not attend. He's accompanied by a girl, Salyer, who he met on the road, and took along with him. "You took a girl you picked up to my father's funeral?" Ben asks, incredulously. "At least she was there," Jeeter shoots back.

As the weekend unfolds, the girl's mother turns up – as do mysterious ghosts from the conflict, vivid to Ben's imagination, and revelations about Jeeter, which cast him in an entirely new light. The play swoops between fantasy and acute naturalism, the conversation between the vocal style of the young Bob Dylan and the importance of Robert McNamara, architect of the Vietnam strategy who regretted his actions – but never apologised. All the players are, in some sense, McNamara's children, grappling with his legacy and the broken dream of a country that his excursion left behind.

There are many twists and turns in the plot, probably too many for so slender a vehicle to hold. Credulity is constantly stretched. And Haidar's direction is so deliberately underpowered, that there are not many fireworks; the pace is leisurely and always the same. Yet the dialogue is witty and the acting engaging. Demetri Goritsas offers a nice line in laid-back irony as Ben, Todd Boyce is convincing as the perfidious Jeeter, and Zoë Tapper touching as Salyer, unbelievable though her character's actions are.

Last of the Boys runs at Southwark Playhouse until 4 June.