Journalist and historian Gitta Sereny's true life account of her interrogation of SS Hauptsturmführer Franz Stangl in a Dusseldorf prison, adapted by former Citizens Theatre stalwart Robert David MacDonald, is an absolutely unflinching journey into the reality of the holocaust.

An unadorned set draws the attention onto the dialogue, with Gareth Nicholls' direction focused on power shifts between interviewer and subject. Sereny (played by Blythe Duff with great dignity and compassion) tries to break the arrogant narcissist Stangl, who seems rocklike in his resolution and unaffected by her questioning strategies.

Stangl is wonderfully portrayed by Cliff Burnett: condescending, brittle, then betraying a small sliver of conscience, he finds justifications for his indulgence while thousands of Jewish and disabled men, women and children are dragged off to the gas chambers. He simply denies his guilt: he was only following orders, the classic Nazi excuse.

The extent of Stangl’s corruption is increasingly apparent, as Sereny's psychological cat and mouse games yield little, instead her own calm exterior crumbles as she tries to maintain a personal distance.

The production has a few weaknesses – Molly Innes as Stangl's wife Thea seems too young and there is a lack of chemistry between the two, yet the central conflict remains utterly, horribly compelling. And Neil Haynes' mirrored set, reflecting the audience back as the lights dim, restates that humanity remains at the heart of the evil.