For a play with such an elegant, poetic title as The Love of the Fireflies (El amor de las luciernagas), I perhaps expected a little less swearing. But, if nothing else, The Love of the Fireflies is real: if a young Mexican woman escapes to Norway after her boyfriend leaves her, naturally curse words, alcohol and frank, funny explorations of sex are going to follow. And, from this piece’s piercing emotional undercurrent, truths will surface.

Showing at the CASA Latin American Theatre Festival, the award-winning Mexican theatre company Los Guggenheim and its founder writer-director Alejandro Ricaño bring British audiences on a Mexican sci-fi roadtrip – who wouldn’t want to see that? In Bergen, Norway (a city that she tells her friend Lola is ugly, but with more colourful language), Maria glimpses her doppelganger on the funiculur to Mount Floyen and faints. She returns to Mexico to find her double is already beginning to snatch up parts of her life. With her friend Lola, she travels across her country and into Guatemala in chase of lost love and her identity.

Maria, played by three women in fitting with the play’s focus on identity, is a fully fleshed-out character I want as a best friend. She is witty, crass and self-deprecating. In a double act familiar to us all, she exchanges insults, worries and laughter with her best friend Lola, with honesty and camaraderie so convincing it is as if Ricaño has plucked two best friends from the real world. The cast are excellent all round, with mesmerising ensemble movements and a gentleness in playing their characters that feels both organic and believable.

“Our love is like fireflies”, says Maria. “Intermittent”, her on-and-off boyfriend Romulo agrees. Mostly, The Love of the Fireflies chooses to bask in the light with humour and charm. Characters loveably snort over sex or toilet humour, Maria explains how she masturbated in a church (to much giggling) and, of course, the swearing is always inventive. But then the tone will slip unexpectedly into that mournful, hopeless and stark undercurrent running throughout, whether about the wider political situation in Mexico, a flood in Guatemala or love. Everything that burns, the play acknowledges, is extinguished.

It is a bizarre show, but enchantingly so. A dizzying journey through Mexico and a glimpse of its culture gives us this playful, at times devastating and, beyond all, truthful exploration of love and identity. What a glowing example of Latin American theatre – a memory for the audience that will be hard extinguished.

The Love of the Firelfies played at the Barbican until 7 October, as part of the CASA Latin American Theatre Festival. For more information, see the Barbican website. Photo: Los Guggenheim.