Sammo and Tyrell are working undercover with some jewel thieves when they are attacked by another group of, heavily armed, thieves. They attack their own comrades and join the new gang so that they can find out who they are, and who they are working for. The new gang specialises in robbing other gangs of criminals which leaves Sammo and Tyrell in a dangerous situation. The MCU have no idea where their two fellow officers are or what they are up to.

A biological virus is unleashed in a police precinct and the whole station is quarantined. Sammo and Tyrell investigate a student who stole the virus from his university by injecting it into himself. While they try to find out where the virus and vaccine is, and who is behind the outbreak, Amy and Grace find themselves quarantined in the MCU precinct when it to is attacked.

A new generation of spy satellite crashes down to earth in downtown LA. The FBI tells Amy that the only missing piece is extremely radioactive. If it is opened it could irradiate half the city. Involved in the bringing down of the satellite are the criminal cult Scorpio and their mysterious leader 'The One'. FBI agent Wick insists that Sammo and Grace are not to be allowed to participate in the case because they are both Chinese nationals and are probably Chinese spies. While this is going on Sammo is also trying to track down the whereabouts of his son, Lone Wei.

The MCU discover that Scorpio began in Shanghai and has a personal grudge against Sammo. 'The One' steps up his campaign to kill Sammo by first dealing with his friends and family. He already has his son as a member of Scorpio and next he kidnaps Amy and her fiancé and buries them alive in their limo. Sammo, Grace and Tyrell have to find out where Amy is before he targets the next one of them.

Scorpio implements its plan to control the world by causing a randomly picked plane to crash. They know that they can now effect any plane, anywhere in the world and the governments of the world will soon be at their control. Meanwhile the MCU tries to find out where 'The One' is running his operation from. Sammo has a chance to capture his son but decides to give him the chance to choose the right path and lets him go.