Infernal Affairs is a Hong Kong crime thriller film and one of the standout films from the city for that decade. The film naturally takes place in Hong Kong and focuses on the police trying to take down a gang who deals in drugs. The police has put an undercover cop inside the gang, while the gang has also placed a mole within the police. Thus the film revolves around the pair as they try to find each other's true identity. The film starts with a tense police operation as we see each of the moles feed information to the other side. As the plot starts kicking, you will wonder how the film will end. It primarily focuses on Yan, who is the undercover cop, and the struggles he is facing when he has been undercover for a whole decade. Comparatively, we also see the stress that Lau, the gang mole who is now an inspector, is dealing with as he has to juggle actual police work while not blowing his cover. Both of their situations are unenviable as it comes to a boiling point as each other's bosses are mounting the pressure to end the battle. The ending will surprise you since it is unexpected (although the random romance suddenly being thrown in your face was a bit surprising too) and it fits within the themes of the film perfect. At only 1.5 hours long, the film is paced very well with nary a dull moment.