Those who fear something may get lost in the translation might want to hang around Hong Kong instead: the sequel–actually, a prequel–“Infernal Affairs II,” is due out Oct. 1. (The third installment, filming now, will be released on Dec. 12.) But even Alan Mak Siu-fai, who co-directed the trilogy with Andrew Lau Wai-keung, has some misgivings this time. “I like all three movies, but I worry about the second one,” he says. “It just doesn’t have enough stars.” The original featured the sharp-jawed Andy Lau Tak-wah (“Fulltime Killer”) as a triad member who infiltrates the police force, and Tony Leung Chiu-wai (“In the Mood for Love,” “Hero”) as a cop who poses as a gangster. But since “IA2” looks at their earlier lives, the characters are played by younger actors, the lesser-known pop idols Edison Chen Koon-hei and Shawn Yue Man-lok. (Lau and Leung return in the third installment, which takes place two years after the original.) In making the trilogy, Mak says he focused only on Hong Kong–not Hollywood. “If there’s one thing I’ve learned, it’s that people just want to see a good Hong Kong movie,” he says. “The last thing they want to watch is Hong Kong trying to mimic Hollywood.” Because then who would Hollywood imitate?