In 1989, Effie Entezari is shot dead. Police convict her estranged husband Mike despite no physical evidence. Their daughter Pooneh refuses to believe he is guilty and makes a promise to her mother to find her killer.
Over 35 years, Pooneh undertakes her own investigation where she uncovers police failings, ignored suspects and new forensic evidence that proves her father's innocence.
A DNA match points straight to former trained killer Viktor Pell. Pooneh's decades of sacrifice pay off as Pell is found liable for her mother's murder, finally clearing her father's name. The verdict brings justice but it comes too late for Mike, who died never knowing the truth.