DCI Jack Parker fights to hide his Early Onset Dementia while he continues to do the job he loves - investigating crimes and bringing villains to justice. Still haunted by the death of a colleague in a hit and run for which he blames himself, he pursues the case with a determination bordering on recklessness when he encourages her replacement, DS Emma Steel, to get close to a local gangster who knows more than he's letting on, thereby endangering Emma and causing dissent among his team.

Jack is called in to investigate the disappearance of a young woman, Maria, and her son who appear to have vanished off the face of the earth. His boss tells him to focus on her ex-husband, but though the evidence points in his direction, Jack has his doubts. The woman has form with toxic men and the husband is just the latest in a long line.

As Jack's plans to hide his condition become more challenging, he begins to wonder if Maria is really the innocent victim she's been portrayed as - until a body turns up. As he starts to discover the truth in both these investigations, Jack comes to understand that nothing in this world is as black and white as it seems.