In 1976, a teenage girl named Annalise Wood disappeared, and though her body was later discovered, the culprit was never found. Decades later, when DNA linked to the Annalise murder unexpectedly surfaces, cold case detective Morris Keene and his former partner, Chloe Frohmann, hope to finally bring closure to this traumatized community. But the new evidence instead undoes the case's only certainty: the buried body that long ago had been confidently identified as Annalise may be someone else entirely. Whose body was unearthed all those years ago, and what happened to the real Annalise? Is someone interfering with the investigation? And is there a link to a present-day drowning with eerie connections?

Just outside Cambridge, a body is discovered floating. The police have little to go on until they find an identity. At the same time, an odd young woman is trying to deliver an unclaimed letter. If she and the police are looking for the same person, how did she get into the water?