Rachel Nickell is murdered on Wimbledon Common on a summer morning in 1992, in broad daylight, with her two-year-old son standing beside her as the only witness.

What follows is not just a murder investigation, but a second ordeal running alongside the first. The police become certain about a man named Colin Stagg and stay certain, running an undercover honey trap operation that a judge later dismantles as one of the worst chapters in British policing history. The media surrounds what little privacy the family has left.

More than a decade later, old evidence finds new eyes, and what it reveals is both a resolution and a reckoning.