Lego City: Undercover is the first game in the series. It is the sequel to Lego City Undercover: The Chase Begins, which was released at a later date for the Nintendo 3DS. Lego City: Undercover is a Lego game for the Wii U that takes advantage of the Wii U GamePad. It cannot be played using a Wii Remote or a Nunchuk. Lego City: Undercover is a one player game and does not support a multiplayer mode.
When you very first begin the game, Chase McCain is arriving in Lego City via boat travel after being gone for two years. He was sent away to do police duty in a different location and is coming back to continue his career where he had originally begun as a rookie. The criminal actions of Rex Fury was one of his first cases. During that time, he started out doing simplistic work, such as buying donuts and finding a lost dog. As things progressed, he became entangled with the crime spree of Rex Fury.
In the present, Rex Fury has finally returned after breaking out of prison and is on the loose again. The police chief, Dunby, does not believe that Rex Fury is anywhere near Lego City and orders Chase not to meddle into the new case of Rex's escape. Chase does not believe that Rex has left Lego City and becomes determined to find him again. This goes against Dunby's direct orders, but Chase, as a famous police officer, has enough of a reputation to defy the police chief and go after Rex anyway.
For almost the entire game, Rex Fury never appears and there is very little to hear about him. It is only towards the end of the game that Chase finally locates Rex. For the rest of the duration of game play, Chase is busy working as an undercover police officer for different, major gangs in Lego City. First is Chan Chuang, the owner of a junk yard full of old vehicles. Chan never has anything to do with Rex. Second is Vinnie Pappalardo, the owner of a fancy ice cream parlor. Vinnie has been working for Rex Fury by stealing him special items of interest, including a robotic dinosaur from a museum and the Bell Pepper Emerald. Eventually, the relationship between them becomes sour, and Rex orders a gang to attack Vinnie at his ice cream parlor. Chase hurries to Vinnie's aid and arrests the attackers. However, all the way to the end of the game, there is never anything heard about whether or not the police department ever decided to arrest Chan, Vinnie, and their gangs. It is assumed that they may have been overlooked in light of Rex Fury and Forrest Blackwell.