One long kiss scene.

Sometimes intense bloody violence.

Corruption police Yeung meets with mobsters in a nightclub and talks to them, while discovering a drug envelope.

A reference to drug trafficking in the mob.

mobsters drink at the bar.

The Infernal Affairs series is a very dark Neo Noir movie series featuring the story of an underworld policeman and a police gangster. The two spies live in the lives of gangster/police officers, and are confused by their identity.