Batman: Arkham Knight

Batman: Arkham Knight is an action-adventure video game developed by Rocksteady Studios and published by Warner Bros. Interactive Entertainment. Based on the DC Comics superhero Batman, being the fourth main installment in the Batman: Arkham series.

Plot
Nine months after the Joker's death, crime rates in Gotham City have dramastically declined, but Batman anticipates a new threat and maintains a vigil over the city. Before his demise, the Joker sent his mutated blood to Gotham's hospitals and several patients were infected. While most were cured, the patients who were not treated are starting to look and act like the Joker. Batman researches a cure for the mutations and orders Robin to watch over the infected.

On Halloween night, Scarecrow unleashes his newest strain of Fear Gas in a diner, and threatens to release it throughout Gotham. Six million civilians are evacuated, but the city's criminals and supervillains stay behind, leaving Commissioner James Gordon and the Gotham City Police Department outnumbered.