Morning

"Locked from the inside, it's impossible to open from the outside, wait for me,"

Elmer withdrew his arm and slid out of bed. He repeatedly checked the tightly shut windows, seemingly finding no issues. He stuck his head out to observe the outside. If it were a human, it would probably be impossible to enter through the window. Moreover, if a person were to squeeze in, they would have to open the window more. Even if the killer was very flat and could enter to commit the crime, why couldn't the coroner find any issues? Was it a lightning-fast death?

"Don't just stand there, I'm scared," 

Shi Yunfei called out.

Elmer looked down along the corners and noticed a small detail. A bit of debris had fallen inside the window, and there was a small hole in the glass, less than two millimeters in radius. Elmer also noticed traces on the lock's surface where something sharp had slid across.