A killer is caught on tape talking about a murder with a mysterious crime boss. Earlier, on a summer's night in suburban Melbourne, a mother of three is stabbed, and her house is set on fire. Firefighters race to the house, but the blaze is too intense. Police begin their investigation close to the home of the victim, Mary Cook.

Journalist Alicia Bridges looks into the case. She will spend years trying to work out what the tape really means, and finding out about the crime boss on it, Mr Big.