Spoiler warning: Spoilers for Season 1 of the dramatized series.
The Watcher does not reveal who sent the letters. Its first season ends with Dean returning to the house after selling it, while Nora secretly follows him. Leaving the property has not ended the surveillance shaping their marriage.
Why does Dean call himself John?
Outside the house, he introduces himself to the new owner under the name associated with John Graff, a figure central to his suspicions. He claims to live nearby and indicates that he will return.
The encounter makes him look like another person whose interest in the property has exceeded any legitimate role there. That resemblance is disturbing without proving he wrote the original letters.
The new owner opens the mailbox as Dean watches. The scene invites another suspicion, but the audience does not see him compose or deliver a new threat.
She speaks to Dean by phone as if she believes his account of being elsewhere. After he drives away, her own car appears outside the house.
Her presence reveals a second layer of watching: Dean has concealed his return from her, and she is checking on him without disclosing it. The family’s attempt to protect itself has become a pattern of mutual distrust.
Their affectionate phone call is therefore not necessarily false. It exists beside behavior neither has made part of the conversation.
Is the ending a solution to the real case?
No. This is the television drama’s conclusion, with fictionalized characters and events. It does not provide evidence identifying a real letter writer or justify accusations against people connected to the source story.
Within the drama, the unresolved identity changes the focus from catching one intruder to recognizing what the fear has done. Dean has surrendered ownership while remaining psychologically invested in the house.
The family can move to a different address. The last scene asks whether they can also stop organizing their lives around the person they never managed to identify.
Sources: official ending breakdown.