To dive deeper into the mystery and the real-life events that inspired it, check out these sources:
In the fifth episode of The Watcher , titled the tension shifts from external threats to internal paranoia as the Brannock family begins to turn on each other. The episode explores the psychological concept that the simplest explanation—in this case, that someone within the house is responsible—is often the right one. Plot Breakdown & Key Reveals
The real-life Broaddus family (the inspiration for the Brannocks) reportedly remained a united front. The subplot of Nora suspecting Dean of being "The Watcher" was created for dramatic tension.
Ellie discovers a Facebook group for former students of an English teacher named Roger Kaplan , who used to have his students write "love letters" to houses. This makes Roger a primary suspect for the origins of the Watcher's poetic and creepy writing style. Fact vs. Fiction
Nora becomes convinced that Dean is the one writing the letters to scare the family into selling the house, especially after discovering his financial struggles and a mysterious video of a girl with pigtails in their bedroom.
'The Watcher' Season One, Episode 5 Recap: 'Occam's Razor”