Time Out says
By far the best of the Czech movies banned when Dubcek was toppled in 1969, this uses a flashback structure to explore a crucial night in the lives of Ludvik, a high-ranking bureaucrat, and his semi-estranged wife Anna. They come home from a reception (at which Ludvik learns that his boss and other government officials have just been arrested in a political purge) to find that their home has been comprehensively bugged. During the long and sleepless night, they tear each other apart with Albee-like ferocity while imagining the worst that the future may hold for them. The dawn brings a twist ending that makes Kachyna's film the bitterest and most scathing account of what it takes to get ahead in a Communist bureaucracy.