An idealistic young official is ensnared in tyrannical Soviet-era bureaucracy in Ukrainian director Sergei Loznita’s superb, slow-burning drama.

Honour and idealism collide with brute force in this masterful work of cinema. The backdrop is the Soviet Union in 1937. Joseph Stalin’s great purges are cutting a swath through the old guard of Communist party members, while an oppressive atmosphere of suspicion looms over everything.

When Kornyev (Aleksandr Kuznetsov), the newly appointed investigative prosecutor for the Bryansk region, learns of corruption in the local branch of the NKVD secret police, he does his duty to his country and his job by the book. But he finds himself in a bureaucratic labyrinth in which every corridor is corpse-grey and every door is slammed in his face.

The film is extraordinary: the measured pace exerts an ever-tightening chokehold of tension, and the period details are brilliantly evoked. And, as with any examination of the savagery of totalitarianism, this story set nearly 90 years ago manages to feel chillingly relevant.