As French colonial rule reaches a violent end in Vietnam, a 12 year old boy makes a treacherous journey in search of his estranged father.

"Ngày Xưa Có Một Chuyện Tình" revolves around the intertwined friendship and love story of two boys and a girl from childhood to adulthood, as they face the challenges of fate. Spanning four stages from 1987 to 2000, the three friends—Vinh, Miền, and Phúc—grow up together, experiencing the innocence of love, life's struggles, and personal growth along the way.

Inspired by Chuyện Người Con Gái Nam Xương and Đèn Âm Hồn, the story is set in a rural village in Northern Vietnam during the feudal era. Thương, a mother raising her son Lĩnh alone while awaiting her husband's return from war, faces eerie events after Lĩnh accidentally discovers a mysterious lantern. The boy begins calling the shadow cast on the wall his father. According to the village shaman, the lantern is a đèn âm hồn, capable of summoning vengeful spirits. Strange and haunting occurrences unfold, leaving Thương and the villagers to question: is the shadow truly Lĩnh's father or something far more sinister?

The story of a circus performer and his son on the journey to find lost connection.