[Six Months Ago]
After seeing off her husband at the airport for a two-days business trip, when a woman named Susan Green returned to her apartment, she barely kicked off her shoes and filled herself with a glass of water when a knock on the door arrived.
Unsure of who it might be at the lunch hour, she opened the door only to find no one outside.
Susan frowned. She was pretty sure she had heard the knock. Not once. Not twice. But thrice. Someone had knocked at the door thrice. Wondering if the kids in the building had once again picked up the bad habit of annoying the random neighbours, she closed the door and locked it.
However, just when she hoped to get back to the kitchen counter and grab herself a glass of water, her gaze fell on the yellow manila envelope on the floor. It looked
