Tsui Chik (Simon in the US version), tries to lead a quiet life as a librarian. However, he is really a former test subject for a highly secretive supersoldier project and part of a special commando unit dubbed "701." The 701 squad is used for many government missions, but after one of the agents kills a team of policemen in an uncontrollable rage, the government decides to abort the project. Tsui Chik is then enlisted to help the remaining 701 agents flee government control by their commanding officer. Tsui Chik does this, but instead of re-joining the team, he goes to live on his own. When he discovers that other test subjects have begun a violent crime spree against the drug cartels that the police are helpless to stop, he sets out to stop them himself by donning a disguise and using the superhero alias of "Black Mask". Having lost the ability to feel pain due to experiments performed on him by the military, Black Mask is highly invulnerable.