Ann Ming is distraught when her 22-year-old daughter Julie goes missing; the police suggest that Julie must have fled to London to reunite with Julie's estranged husband, but Ann knows that Julie would never leave 5-year-old Kevin behind.

Haunted by nightmares of her daughter's death, Ann channels her grief into pressuring the police for answers while trying to save her marriage; when the jury fails to reach a verdict, the judge calls a retrial and Ann must relive the ordeal.

At the retrial for Julie's murder, the jury fails to reach a verdict and Julie's killer walks free; he brags about how he got away with the "perfect murder," knowing he is protected by the double jeopardy law, but Ann is determined to get justice.

Determined to overturn double jeopardy, Ann takes her fight to the Home Secretary and the House of Lords; the law is eventually repealed, and Julie's killer is finally convicted of murder and given a life sentence at the retrial.