Let me draft an outline. Protagonist: A young woman, maybe a journalist or someone with an investigative streak. Antagonist: A shadowy figure from her past or a corrupt corporate figure. The window could be a way she gathers clues or witnesses something she shouldn't. Maybe she moves into a new house where the previous occupant had a mystery. Or she starts receiving messages that lead her to investigate through windows. The part 1 could end with her getting a death threat or someone after her, setting up part 2.