Z. B. (24) has failed an important exam for the third time. Her possessive and ambitious mother N.B. (55) will not let it go that easily - not this time. Z.B. phones her acquaintance B.S. (28) and asks him for a small but dangerous favor. On the verge of despair, Z.B. feels that her mother's actions have brought her to the brink... Once Upon a Winter's Night is a film mosaic of shocking human destinies in a fashionable Zagreb neighborhood in midwinter. Christmas carols become the creepy and disturbing soundtrack to an unplanned murder. The film makes full use of documentary-style directing and a story that feels as if it has been ripped from a newspaper's crime pages. It is the story of a gun looking for its owner.