When siblings Ava and Luke discover a mysterious box of papers in their dad's attic they are instantly intrigued. And, as they read through letters, diary entries, newspaper cuttings and notarised secret recordings, they realise that a decades-old, still unsolved, murder case is unfolding right in front of them . . . Determined to discover what really happened, Ava and Luke turn detective to try and crack the case. But soon they realise that the killer might still be out there - and might be closer than they think... YOU know the facts. YOU have all the clues. Can YOU solve the mystery before they do?