Director Marco Mak pays homage to Infernal Affairs with his new undercover cop movie Wo Hu, a crime/police thriller produced by Wong Jing. Wo Hu has made obvious references to the blockbuster which has lead to a resurgence of the undercover theme in Hong Kong cinema. Eric Tsang, Francis Ng, and Shawn Yu from the Infernal Affairs join forces with Michael Miu, Jordan Chan, and Julian Cheung in this serious yet entertaining movie. Instead of portraying the lives of undercover cops, Wo Hu details how the downfall of a triad organization can be attributed more to the gangsters' human weaknesses than undercover operation.

Veteran Michael Miu stars as Police Chief Wai who dedicates himself to combating the triads. However, finding evidence to prove the triad leaders' crime is no easy task, and sending undercover cops do not help much. While triads get the news about the massive undercover activity, triad leaders Jim (Eric Tsang), Walter (Francis Ng), and Tommy (Julian Cheung), each running a certain business for the low-profile triad head (Yueh Hua), do not quite believe it as a threat. But when Tommy almost get caught, the triad leaders, including the rising Fei (Jordan Chan), start to worry about their own established interests. Wai is indeed quietly observing their internal conflicts and planning to strike back...