The last time Chilean theatre director Juan Carlos Zagal's Teatro Cinema company appeared at Edinburgh International Festival in 2010, they brought some very dark materials indeed.

That was Sin Singre (Without Blood), adapted from a novel by Italian writer Alessandro Baricco, and an original piece, The Man Who Fed Butterflies.

Now they return with the final part of their trilogy, Histoire d'amour, this time adapted from Regis Jauffret's novel about a quasi sado-masochistic relationship between an English teacher and a woman he sees on the underground.

"Histoire d'amour is a tragic story of two people searching for love who get lost in a dark labyrinthine abyss," according to Zagal. "Their souls get lost and sink because they cannot find a way out of this encounter that condemns them. This is a story that shows the emotional instability of many of us nowadays, where the masculine side is strong, and exerts a strong influence over the feminine principles of receptiveness, mysteriousness and creativity.

"If there is no such balance between both these principles, we turn into mindless people. This is an obsessive story that points out all we ignore about love and tolerance, and is very graphic at times.

"It shows how we as human beings can act towards the people around us, which makes impossible the union, communication or whatever we understand is the meaning of living together as a couple."

As with all Teatro Cinema productions, the really interesting element comes in the telling.

As the company name implies, Zagal, art director Laura Pizarro, designer Luis Alcaide and multi-media director Montserrat Antequerra have created a unique fusion of film and theatre techniques that synchronises live performers with projections that allows the action to flow into more panoramic scenarios than mere scene changes allow.

Given the noirish sensibilities of the company's two previous works, Histoire d'amour wasn't a natural choice for Teatro Cinema, and even at this stage Zagal expresses reservations.

"I don't know if it is right for Teatro Cinema," he says, "and remain doubtful. It was pure intuition that made us choose it in the hope it would lead us somewhere.

"The novel is related from a personal point of view. It seems like a long monologue that strongly describes the psychotic state of mind of one of the people involved. We noticed its powerful drama and its cinematographic synthesis. The play is a trip to hell. It holds the people as prisoners and gives them no break, condemning their souls. This made us investigate mental illness and disorders in sexual behaviour, from a state of euphoria to the deepest depression. From light to darkness, a life full of violent contrasts."

Histoire d'amour's place in the trilogy may seem tangential, but Zagal takes a more lateral view of how they sit together.

"All three pieces take place in cities," he says, "and they are all very solitary and labyrinthine. In all three, as well, there is that energy we call love in the meeting between a man and a woman. In all three, there is the journey in time and space of the story and the characters as in movies and in literature."

With technology so crucial to the Teatro Cinema experience, the company's approach has moved on considerably since the last Edinburgh visit.

"We've improved in the use of stage utensils in combination with virtual settings and in the relationship between actor and video, to achieve a greater fluidity."

Beyond such melding of forms to create a new theatrical language, however for Zagal it is the story itself that matters.

"We wanted to begin a journey to the dark and hidden side of ourselves," Zagal says,"and here we are, with a boat as a nutshell in a rough sea, a little stranded, and trusting our theatrical experience to end the journey."

www.eif.co.uk/histoire

Histoire d'amour, King's Theatre, today to Saturday at 8pm; Saturday matinee at 2pm.