Witness Protection
The man in question was in the witness protection program. Many people wanted him dead, so he rarely left the house. That applied to his daughter, and she often watched the neighbors from the windows, but things had changed.
Noticing a Detail
When the FBI checked on him, they noticed the girl staring out the window. It was a small detail, but the man’s associate had also been in the area. If they had seen the young girl, it could blow their cover, so the FBI had to take action.