Anxiety about new technologies and nostalgia for old ones have propelled letter writing to the centre of the literary stage. There have been books (Letters of Note, To the Letter) and events (World Book Night's Letters Live). Now comes Letters Home, a promenade performance of four epistolary stories commissioned by the Edinburgh international book festival and performed by Grid Iron in a series of rooms around Charlotte Square.
It begins at the festival site, where we're dragooned into four colour-coded groups to be led off on separate circuits. First stop for the burgundy group is a bedroom, where two young women lie asleep on a bed. They are Chisara and Oyin, who awake to find their holiday romance interrupted by Oyin's return to her husband in the US. Chimamanda Ngozi Adichie's story, Details, unfolds in emails between the lovers. Left behind in Nigeria, needy Chisara obsesses about a bottle of bath salts in the bathroom of cosmopolitan Oyin's marital home. This domestic detail channels the sexual jealousy of a woman who knows nothing of her lover's other life. Their whirlwind romance left Chisara – "We didn't talk about the after" – and the audience uncertain as to whether this is a love story or a tale of sexual tourism.
The next story sits us beneath four screens, on which are projected the locations of two Punjabi soldiers in the first world war. While Wahid convalesces in a Brighton hospital, Qasim struggles to make sense of the desert war in Mesopotamia. When Wahid settles back into civilian life among the mustard fields of his homeland – "I have lost a leg, but gained a pension" – Qasim's questioning leads him to a grimmer fate. Written by Kamila Shamsie and directed as a film installation by Alice Nelson, War Letters movingly channels key themes of the great global war: comradeship, betrayal and the continental carve up that created the mess of today's Middle East.
The most strenuously theatrical of the quartet is also the most baffling: Christos Tsiolkas imagines a correspondence between Eve and Cain, who has been sent into exile after the murder of Abel. Across a sand-strewn stage they rant at each other through the alter egos of slave messengers. Charlene Boyd convulses with the rage of the eternally wronged mother, while Gavin Marshall's Cain/ bondsman agonises over how to honour his dead brother without shackling himself to his crime.
It's symptomatic of the show's powerful symmetries that the distress of Cain and Eve sounds a distant echo in the stylistically different fourth piece. Seated in aeroplane seats, blindfolded, we hear an email exchange between two Jamaican women about a young man who has gone into his own sort of exile. What are Maxine and Nicky, the wryly disapproving correspondents of Kei Miller's story, if not the messengers of the internet age, carrying stories of an estranged mother and son across continents?
At a time when the fringe is muscling into spoken-word territory, Letters Home is a fabulously stylish counterstrike for the book festival, creating a new platform for the short story, while examining the theatrical potential of narrative. A post-script scene shows the four actors changing back into their real selves. The illusion they have created is so capacious that I am momentarily confused as to why there are so few of them.
• Until 25 August. Box office: 0845 373 5888. Venue: Charlotte Square, Edinburgh.
