A leaves the main door to the apartment open, knowing that anything could happen.
B confronts A.
B: Hey, can you don't leave the door open like that? It has happen many times already and I am sick of closing the door for you. Do you know the potential danger if there is bad people? They might just come in and rob you.
A: Even if the door is locked, things still disappear in this house. I prefer to think that strangers came in to steal them than my housemates. *STARE AT B*