Harley Quinn and Poison Ivy, after escaping from Arkham Asylum, continue Ivy's search for the Zombie Root, a rare plant in the Central American jungle country, Costa Verde. The only problem is that the country's corrupt president, Juan Ceballos, and industrial rainforest loggers get in their way.
Costa Verde soldiers nab Harley and Ivy shortly after they set foot in the country. In a jail sturdy and rough police women, who are aware that Ivy's pheromones work only on males, brawl with Harley and Ivy. The quick thinking Harley again demonstrates her excellent hand-to-hand combat skills and defeats both of the brutal police women. Ivy then admits that her pheromones won't work on females, but her poisonous toxins work equally well on both males and females. The brawl stops when soldiers storm into the jail cell. They escort Ivy and Harley away at gunpoint.
Costa Verde President Juan Ceballos greets Ivy and Harley. He learns from Harley that Ivy is planning to distill the Zombie Root. When Juan Ceballos demands to know the refining technique, Harley tricks him into getting close to hear the supposed secret. Harley suddenly grabs his tie and hurls him against Ivy's lips. Ivy's kiss causes Juan Ceballos to fall under Ivy's trance. He gives them an armed vehicle to drive through the jungle.
As they drive through the jungle, Ivy warns Harley to drive carefully to avoid hurting the jungle plants. When Harley asks about the monkeys in the way of the Sport Utility Vehicle, Ivy shows no concern for the monkeys' safety.
Ivy and Harley encounter two tough loggers who block their path. Ivy pushes a button on the armed car's dashboard and fires a Stinger missile, which explodes near the loggers. Harley drives away.
Ivy finds one of the long sought Zombie Root plants, carefully removes its roots and soil from the earth, and places it in a pot. She is delighted at the green environment and is thrilled when jungle vines entangle her.
Harley, however, fights off the mosquitoes and wishes to go home.
Before Harley and Ivy can leave, the two loggers again encounter them. Now very angry, the loggers try to kill Harley and Ivy. Harley uses her acrobatic and hand-to-hand skills to defeat the lumberjack who has a chainsaw. Meanwhile, Ivy uses her ability to command plants to entangle the other logger. Then, she uses her scientific knowledge of poison arrow frogs in the swamp mud to paralyze the other logger before he can use his flamethrower. Harley and Ivy then escape.
Before leaving Costa Verde, Ivy telephones President Juan Ceballos, who is still entranced from Ivy's pheromone kiss. Juan agrees to protect the country's rainforest and even designates a special preserve area, naming it the Isley and Quinzel Botannical Reserve, a haven for rare and endangered plant species.
As the story closes, Alfred and Batman, in Gotham City, comment on a newspaper report about Harley's and Ivy's Costa Verde adventure. Batman implies that he will hunt down and capture Harley and Ivy if they return to the USA.