Old Zhou had been staking out Panjiayuan for thirty years, but that afternoon he was startled by a young delivery person.

The young man's name was Chen Rang. He was holding a bronze incense burner, saying it was given to him by his adoptive mother on her deathbed—the only keepsake left by his biological father. His adoptive mother had only spoken three words: "Fulong Zhi," and then she passed away.

At the bottom of the incense burner was engraved "Dan Yuan." Old Zhou stared at those two characters, his hand trembling slightly. He grabbed Chen Rang and pulled him deep into the alley, then knocked on a weathered old door.