Nukem's radioactive presence at a leaking nuclear power plant triggers a meltdown.

Wheeler is stranded on an island of humanoid mice on the brink of population overload.

To make a fast buck from a trash strike, Sly Sludge steals an untested microbe from Gi's scientist hero, Dr. Helix. It was supposed to be a technological fix for the problem of overflowing landfills, but it simply absorbs trash to become a city-devouring garbage blob. The blob must be stopped before it grows out of control.

In the Florida Keys, Ma-Ti has a brush with what he thinks is a giant man eating shark, though Gi reveals that it is a harmless Basking Shark. When a local overhears and misinterprets their conversation, panic spreads throughout the resort town, whose mayor then hires Argos Bleak to eradicate all the sharks in the bay. Then, when stinging jellyfish (that the sharks used to feed on) swarm the beach, the townspeople learn that predators have an important role in the ecosystem. After escaping their sinking EcoCopter that was shot down by Bleak, the other Planeteers rescue Gi and Ma-Ti (who were captured earlier by Bleak) . . . and the Basking Shark . . . from bloodthirsty Bleak.

While the Planeteers learn about organic farming, Plunder exploits Joe, a man who cannot read, by tricking him into signing a contract allowing the distribution of pesticides on a farm that he manages.

The Planeteers return to Kwame's homeland, Africa, to investigate strange happenings with cattle that was reported by his long-time friend and brother figure, Dr. Mabutu. Little do they know, Dr. Blight is there, scheming to convince a tribe leader (also a friend of Mabutu) to allow the injection of a serum that turns bulls into super steers in order to resolve their meat supply woes. Not only does this threaten the condition of the land, via excessive grazing, but the serum causes awkward side effects, which eventually does wear off. The Planeteers, with a hand from Captain Planet, manage to rid the land of Blight and MAL.

Dr. Blight, who is doing inhumane experiments for a makeup company, is troubled by the Planeteers and the makeup company's owner. Dr. Blight tries to use them as her guinea pigs.