By accident, the three little marsus end up in Felicia's new tire factory. This new edifice, built right in the heart of the jungle, is entirely automated. Using a system of tubes and pipes, sap is sucked out of the neighboring rubber trees, which drains all the life out of the trees and destroys the surrounding forest. At first delighted by the capture of the three baby marsus, Blueprint and Stroy quickly grow disenchanted when they find themselves under siege by a furious Marsu, determined to break down the factory to get his kids back - But, try as he can, Marsu can't destroy the ultramodern factory. Hector studies the building and finds a way to sabotage it by exploding a giant rubber bubble within it. The explosion frees the little marsus and buries the factory under a thick layer of sticky rubber.

Felicia Devort sends an autonomous, intelligent robot, the Deforestator, into the jungle to destroy the forest at high speed. After a violent encounter with Marsu and Hector, the robot starts emitting squeaking sounds very similar to the famous marsupilami "hoobah" - As a result, Marsu becomes convinced that the robot is a friend, and he invites it home--much to Hector's dismay! Before his horrified gaze, Marsu and his family adopt the robot and have a great time with it!!! Eventually, even Hector is won over by the robot, which replants the trees it uprooted... But at night, the Deforestator is obliged to return to the Devort estate to recharge its batteries. Once there, Blueprint, who figures out what happened, reprograms the robot as a Trojan horse... Hector and Marsu manage to defeat the robot and tinker with it themselves, before sending it back to its creator with a new mission.

Lord Judkins arrives in the jungle. He is sent by the Geographic Museum, Diane's employer, to verify that Hector is being properly educated. If he determines that Hector is not being correctly schooled, he will have him sent back to England, to attend boarding school. Our young hero is going to have to be on his best behavior and must prove he's learning and blooming in the jungle. But Hector and Marsu find an ancient Pre-Palombian temple in ruins in the jungle. It's built on a powerful electromagnetic zone. They are struck by a powerful magnetic disturbance, and Hector suddenly believes he's a - marsupilami !!! For Judkins, the decision is clear: Hector must be taken back to civilization. But Marsu doesn't see it that way. Figuring out the connection between the temple ruins and the magnetic pull of the area, he takes Hector back there to reverse the process, much to the distaste of Lord Judkins.

While taking a walk through the Palombian jungle, Marsu falls down a hole into Felicia Devort's new, partially constructed sewers. Unfortunately, not only are the sewers not fully completed, but they've already started to be used. They're full of a highly toxic waste which quickly bubbles to the surface. Poor Marsu climbs out covered in a repulsive, stinky, green slime. All the other animals in the jungle flee at the stench and the sight of our poor hero. Hector and Aunt Diane try to wash the slime off him as best they can, using all the means at their disposal, but the sticky substance won't come off. It's so bad that even Mrs. Marsu and his own children don't recognize him. Meanwhile, in front of a gathering of various ecological groups, Felicia declares Marsu a lethal ecological menace to all of Palombia!!! Quickly understanding what's afoot, Hector comes to the rescue and saves his friend's reputation.

One morning, Hector and Marsu wake up to a disagreable surprise: they--and a big part of Palombia--are beneath an enormous bell jar. It's another one of Blueprint's schemes to imprison Marsu so he can raze the forest in peace. Stuck under the glass bell jar, our heroes suffer from the increased greenhouse effect... With no wind, the Leekysoupi doesn't move, it's blocked off by the glass jar; Aunt Diane's plants dehydrate... The only solution comes from the Leekysoupi. The river starts to produce an algae which eats glass and turns it into sand. Hector and Marsu construct a hot air balloon and they take the algae up to the summit of the bell jar... The algae attacks the glass and in no time, our heroes are free in time to deliver a lesson to Stroy and Blueprint.

On Felicia Devort's orders, Stroy and Blueprint bury toxic waste in the jungle. Marsu eats a contaminated piranha and rapidly gets sick. Weak and incapable of defending himself, Marsu becomes an easy target for Stroy et Blueprint, when they return to the scene of their crime to cover up the evidence of their wrongdoing. Yes, the two numskulls have struck again: when they buried the barrels of toxic waste in the jungle, they forgot to remove the Devort logo! When they see Marsu's weakened state, Felicia's two henchman think they've found the key to their victory... But they don't count on Hector's ingenuity, Aunt Diane's genius at devising antidotes, and Mrs. Marsu, always ready to come to her husband's rescue.