His son was a national junior championship in kung-fu. While knowing his
mission is tracking down a criminal boss in Hong Kong, he fake his crime for
a undercover identity in Hong Kong. He eventually got close with the boss.
On his first criminal case, he got shot by a reporter. A policewoman noticed
and went all the way to China to check his records. While knowing his
background and came close to Jet Li's family. She and his kid fought their
way back to Hong Kong with the letter of his dead mother(which is where the
title comes from). On the other hand, when Jet got closer and closer, it
became far more dangerous while his identity was exposed.