From 1948-1967, Ingeborg Bachmann and Paul Celan, two canonical German-language poets, exchanged letters, a correspondence that coalesced into an intense, long-distance, epistolary romance. Both were members of Gruppe 47, an informal society of German-speaking writers, and their associates included Heinrich Böll and Günter Grass.

The strange affair ignited just after the end of second World War, which cast a lengthy shadow on the relationship. Celan, a Romanian-born Jewish poet, lost both his parents in the Nazi genocide and spent years in a work camp. Bachmann, an Austrian poet and dramatist, was the daughter of a retired and unrepentant Nazi.

Drawing on their respective poems and some 200 letters, documentarian Ruth Beckerman has created a clever, vaguely experimental format in which to explore this tortured romance. Laurence Rupp, a popular Viennese actor, and Anja Plaschg, an experimental musician better known as Soap&Skin, record the writings of Bachmann and Celan in the Funkhaus, an iconic Austrian radio station and theatre.

It is almost like watching a filmed radio play, with the breaks – in which the performers roll cigarettes and exchange banter – providing intriguing footnotes.

Rupp, the more experienced thespian, gives plenty of emotional welly, but its Plaschg’s raw, sleepy monotone, shaking and occasionally breaking, that makes the project truly mesmerising. Her own, austere piano compositions play in the background, as if her heartfelt response needed further amplification.

The Dreamed Ones is almost certainly too cerebral and specialised to appeal to anyone who doesn't have an academic interest in the Holocaust or German poetry. But, given a chance, it makes for hypnotic viewing.