It all starts with the disappearance of a nine-year-old boy, Robert Cleeve-Dufresne. Missing child is found... hung from a tree bitch in the courtyard of his own home. The killer left no trace, and the investigation comes to a standstill. The family is crushed: the mother plunges into herself, the father leaves. After ten years, the boy's sister, who was only two years old at the time of the murder, decides to find and punish the culprit. She "calculates" the criminal and thinks over a plan of revenge.