Criminal Investigation: Notes on Chasing Killers

Today, the police received a mysterious letter. On the pure-black envelope, red lettering read: "To the Criminal Investigation Division, Xishi Public Security Bureau." On the black paper inside was a large "X" symbol. In this day and age, was someone really playing a prank on the police? "Is X pronounced 'ex' or 'cross'?" muttered Nan Huai, a newly appointed detective, as he stared at the symbol.

This novel and its characters are entirely fictional. Any resemblance to actual people or events is purely coincidental. Do not imitate.