When a shocking double homicide goes unsolved for 16 years, a detective teams up with a genealogist to catch the killer before it becomes a cold case.

Using the latest developments in forensic science to uncover new evidence, a specialist team of cold case detectives from South Wales Police are determined to finally get justice for six-year-old Carol Ann Stephens.

Veronica is 30 years old when she disappears. At home in the apartment in Högsbo in Gothenburg, 3-year-old Marcus is waiting for his mother. Today Marcus is 22 and is looking for his father. In the wake of the parents' love story, the mystery grows and discovers a dramatic tangle of events in China, Thailand and Sweden, with disappearances and murders.