The Tywi Estuary Killings

Is it revenge or is it justice? DI Gravel is supposed to be on mandatory leave, but when a severed head washes up on the estuary beach his holiday is cut short. Back on the job, he's shocked when the case leads him to the victim from an old case Seventeen years ago, the system failed Rebecca. They let the abuser of a six-year-old girl walk free. But she's all grown up now and taking the law into her own hands. Is this one killer DI Gravel doesn't want to catch?