Plot
Carl Thorne is released from prison and goes to see billionaire criminal mastermind Lex Luthor, with whom he previously had interactions. Luthor dismisses Thorne, distrusting him due to his troublesome past. Thorne retreats to a bar, where he gripes about Luthor and blames his failures on his ex-wife Susan Linden. Meanwhile, Linden—the superhero Black Orchid—is killed while spying on Luthor's organized crime syndicate; afterward, Luthor's employee Mr. Sterling discovers she is a plant hybrid.
Elsewhere, an amnesiac young girl, Flora, awakens in a greenhouse. She wanders into a nearby house, where she meets Philip Sylvian, who recognizes her as Black Orchid. Sylvian explains that he and Linden were once romantically involved, but separated at the wishes of Linden's abusive father. Linden married Thorne, while Sylvian, Jason Woodrue, Pamela Isley, and Alec Holland worked together on advanced botanical biochemistry that led to Flora's creation; she is genetically Linden's sister. Only Sylvian remains his old self: Woodrue was incarcerated in Arkham Asylum; Isley became Poison Ivy; and Holland was allegedly murdered.
Flora falls asleep afterwards, and experiences Linden's memories in her dreams. Sylvian visits Linden's room, only to be attacked by Thorne. Thorne beats Sylvian and accuses him of stealing Linden from him. Thorne proceeds to the greenhouse, where he discovers statues of Linden. Thorne begins to destroy the statues before another girl—who insists on being called Suzy and also shares Linden's memories—appears. Thorne calls Luthor, who reluctantly comes to the scene. Luthor discovers that Sylvian died of his wounds and orders his men to throw Thorne in the nearby river. Flora saves Thorne before departing with Suzy; Luthor orders his staff to search for more like the girls.
Flora and Suzy travel to Gotham City, the location of Arkham, to converse with Woodrue. The girls are told that Woodrue left the asylum and denied access. Suzy goes to Slaughter Swamp, where she is kidnapped and sold to Luthor. Flora meets Batman, who deduces that she is related to Linden and gets her into Arkham. The Mad Hatter brings Flora to Isley, who is being held there. Isley explains her involvement with the other scientists but refuses to tell Flora who she is. Frustrated, Flora leaves, fails to save Suzy, and retreats to a graveyard.
Batman tells Flora that Holland is still alive and lives in the Louisiana swamplands. Black travels to Louisiana, where she meets Holland, who is now Swamp Thing. Holland explains to her that she is a reincarnation of Linden: Thorne murdered Linden, and Sylvian used her DNA and an orchid to recreate her as Black Orchid. When Linden was killed, another Black Orchid, in this case Flora, awoke.
Using their connections to the Green, Holland shows Flora where Suzy is located, and Flora saves her by knocking down a tree to stop the truck she is held in. The two escape to the Amazon rainforest, but Luthor tracks them and sends Sterling and a team to find them. While searching, Sterling's men are ambushed by Thorne as they approach the girls. Flora attempts to stop the fighting, but Sterling shoots Thorne in the chest. Thorne's death angers Flora, who sends Sterling off with a warning: if Luthor tries to interfere with her again, she will retaliate. Sterling and his men part ways, and Flora and Suzy fly back home.
