Five years after the events of Batman: Arkham Knight, A.R.G.U.S. director Amanda Waller (Debra Wilson) creates a task force known as Task Force X / Suicide Squad, which is composed of Arkham Asylum inmates Harleen Quinzel / Harley Quinn (Tara Strong), Digger Harkness / Captain Boomerang (Daniel Lapaine), Floyd Lawton / Deadshot (Bumper Robinson) and Nanaue / King Shark (Samoa Joe), for a covert mission in Metropolis. Only when they arrive in the city do they realize the severity of the situation: Brainiac (Jason Isaacs) has invaded Earth and has started brainwashing its inhabitants, including Justice League members Clark Kent / Superman, Barry Allen / The Flash (Scott Porter), John Stewart / Green Lantern, and Bruce Wayne / Batman (Kevin Conroy). Waller assigns Task Force X with killing the Justice League to stop Brainiac before he takes over Metropolis and the world.

Five years after the events of Batman: Arkham Knight, A.R.G.U.S. director Amanda Waller (Debra Wilson) creates a task force known as Task Force X / Suicide Squad, which is composed of Arkham Asylum inmates Harleen Quinzel / Harley Quinn (Tara Strong), Digger Harkness / Captain Boomerang (Daniel Lapaine), Floyd Lawton / Deadshot (Bumper Robinson) and Nanaue / King Shark (Samoa Joe), for a covert mission in Metropolis. Only when they arrive in the city do they realize the severity of the situation: Brainiac (Jason Isaacs) has invaded Earth and has started brainwashing its inhabitants, including Justice League members Clark Kent / Superman, Barry Allen / The Flash (Scott Porter), John Stewart / Green Lantern, and Bruce Wayne / Batman (Kevin Conroy). Waller assigns Task Force X with killing the Justice League to stop Brainiac before he takes over Metropolis and the world.