A woman's body found floating in the Thames leads Nikki and Jack to a community on the banks of the River Lee. Three years ago a teenager called Ruth Tresize went missing from the area, leaving the locals haunted by suspicion and grief. A fresh spate of killings reopens these old wounds.

Nikki is under fire for leaking information on a suspect, and Thomas is called in to play peacemaker. Jack and DI Ashton track down the mystery witness. Before the killer strikes again, the team must uncover the true story of Ruth Tresize's disappearance three years earlier.