The first game, Batman: Arkham Asylum (2009), focuses on Batman trying to prevent the Joker from destroying Gotham City after he takes control of Arkham Asylum, and he is forced to contend with numerous other villains he has incarcerated along the way. The second game, Arkham City (2011), is set a year later, after Professor Hugo Strange expands Arkham into a massive super-prison enclosing a neglected segment of Gotham City; Batman is incarcerated and must uncover the secret behind Strange's sinister scheme, "Protocol 10", while slowly dying from an illness inflicted by the Joker. The third game, Batman: Arkham Origins (2013), serves as a prequel set several years before Arkham Asylum, in which a younger and less-refined Batman must deal with eight deadly assassins contracted to kill him by crime lord Black Mask on Christmas Eve, while also encountering the Joker for the first time. The fourth installment, Batman: Arkham Knight (2015), is Rocksteady's conclusion to the series. Set one year after the events of Arkham City, Arkham Knight sees Batman facing Scarecrow along with the mysterious Arkham Knight (and his militia), who have seized control of Gotham City in a plan to destroy Batman, both physically and mentally. The franchise has also seen the release of various mobile games, and the virtual reality game, Batman: Arkham VR, which was once again developed by Rocksteady.