A.R.G.U.S. operative Amanda Waller decides to assemble Task-Force X due to the expanding superhuman community, offering supervillains reduced sentences in exchange for performing suicide missions for the United States government. She selects Harley Quinn, Deadshot, Boomerang, Killer Croc, El Diablo and Slipknot to integrate the team and has them transferred to Belle Reve Penitentiary.
Deadshot is a former military sniper turned hitman to cover his daughter's medical expenses. He is confronted by Batman while targeting a mobster and Batman volunteers to cover Deadshot's daughter's treatment if Deadshot willingly surrenders, which he does.
Batman also interrupts a deal between the Joker and weapons dealer Monster T and rescues Harley Quinn when the Joker abandons her afte their car falls into the river. The Joker then decides to get Harley back.
El Diablo is a former enforcer for a Los Angeles gang who has become a pacifist and doesn't want to use his powers anymore. Killer Croc is a cannibal who lives in the sewers, and Boomerang and Slipknot are amoral mercenaries. Batman captured them all in the past.
Rick Flagg is assigned to lead the Suicide Squad, with Katana as his bodyguard. Flagg is a military man and a loose canon with a history of insubordination, while Katana is a silent warrior who wields the Soultaker, a magic sword that traps people's souls, and seeks redemption for her late husband's crimes.
Meanwhile, adventurer June Moon, Flagg's girlfriend, is sent to investigate reports of supernatural activity in Europe by Waller, who believes these reports could be misinterpreted signs of extraterrestrial activity on Earth. June ends up being infected by the Enchantress, an ancient feral witch, whose heart is aprehended by A.R.G.U.S and kept in Waller's possession.