Editing Infernal Affairs (section)

===Writing===
Writer [[Alan Mak (director)|Alan Mak]] had long wanted to write a story about police and gangsters. The script of ''Infernal Affairs'' was inspired by [[John Woo]]'s ''[[Face/Off]]'' (1997) but Mak knew that its science fiction elements were too implausible in reality, so he focused on the exchange of identity and psychology between the two leads<ref name=":0">{{Cite web|title=《无间道》借鉴于吴宇森的《变脸》|url=https://k.sina.cn/article_2849066081_pa9d14c6102700ryt5.html?from=ent&subch=oent|access-date=2021-12-27|website=k.sina.cn}}</ref> as its themes. In the process of Mak's creation, his good friend [[Felix Chong]] also encouraged and supported him. The script, written by Mak and revised by Chong, took three years to complete.<ref>{{Cite web|title=《无间道》之父麦兆辉：这剧本我写了3年，找了很多人都不愿意拍_腾讯新闻|url=https://new.qq.com/rain/a/20200417A0M9FU00|access-date=2021-12-27|website=new.qq.com}}</ref>

The dialogue in the famous rooftop showdown was created on the spot by Felix Chong and Tony Leung, with Chong playing Andy Lau's part. The script originally included a typical shootout in the third act, but Leung insisted on turning it into a dialogue scene.

[[Gordon Lam]] did not receive the full script and did not know his character was also a triad mole until the final scene.<ref name=":0" /><ref>{{Cite web|title=刘德华谈《无间道》：我不知道全部剧本，林家栋以为自己是警察！|url=https://new.qq.com/omn/20190711/20190711A0T7RH00.html?pc|access-date=2021-12-27|website=new.qq.com}}</ref>