Early Frost (1982)

Private Detective Mike Hayes (Guy Doleman), is working on a divorce case, when he stumbles upon a series of cover-ups that leads to a corpse. His investigation takes him into the lievs of two families living in the Sydney suburbs. Although they look like ordinary people, one of them is the killer. Hayes meets the strange teenager David Prentice (David Franklin), who keeps a violent crime scrapbook, and Val Meadows (Diane McLean), the mistress who believes that someone is trying to kill her. The more the investigation deepens, the more twisted and complex it becomes. It appears the only people who hate Val enough to want her dead, are her own family. Could it be her two sons, alienated by her dominant nature, her lover, or even her best friend?