Walter plays Jimmy Tsen, one of Wo Fat's henchmen. His character's name is not mentioned in the show; it is in a copy of the script for this show that I have. In the first video, while Wo is giving a lecture to a class at the university, Walter and this other guy named Harry Luk go to the basement in the building to tap into a Bunsen burner line so that people experimenting in a lab with a deadly toxin will be knocked out using "V9" gas. After Tsen checks the gas line with a meter which reacts, you can hear him say "This is it." (This line is attributed to him in the script.) In the second video, which takes place the next day, once people -- a professor, two students and an HPD guard -- are knocked out by the gas, Walter and Luk return wearing gas masks, steal the toxin and engage in a battle with cops using machine guns before they escape.
Click on the arrow in the videos below to watch them.
Walter is also seen very briefly around 14 minutes into the show picking up Wo Fat at the airport in a limousine. This is also mentioned in the script which I have.