On my first night in a new apartment, I received a note from the building manager: “No matter what you hear, absolutely do not open the door for your neighbors.”
I followed the rule carefully and made it through the first week alive.
On the seventh day, I found another note from the manager: “I was away last week. If anyone gave you a note pretending to be me, run immediately!”
Just then, someone knocked. “Hi, I'm returning the cookies you left outside my door last week...”