Chu Lin was a mortal henchman working for the Immortal, Kiem Sun. It was he who was in place to judge the effectiveness of Kiem Sun's compounds on a human. Test subject, Gary Correll tore apart the Diamond Mart, and collapsed, begging for help, while under the influence.
Kiem Sun, however, told MacLeod that Chu Lin had stolen his entire supply of quanla root potion, and disappeared two week previously. Chu Lin's plans included using the potion on a biker gang in order to steal a safe full of diamonds from the same Diamond Mart Gary had trashed on the trial run.
Kiem Sun confronted Chu Lin and demanded the return of the potion. When Chu Lin tried to run, he was stopped by MacLeod, who engaged him in a duel, complimenting Kiem Sun on training the young man well.Once he had disarmed, Chu Lin, the young man told MacLeod that he knew about immortals, and that his head would be no good to him. MacLeod countered that he didn't want his head, but a confession that he had drugged and murdered Gary.
At that point, Kiem Sun, attacked and killed Chu Lin, "Forgive the intrusion, but he was mine!"