It seems simple enough for David and Jem to release the two baboons from the experimental research station where they are doomed to die. But when they discover the baboons are no longer capable of looking after themselves in the African bush, David and Jem are forced to stay and protect them. And that's when their problems truly begin....

Saving hundreds of rats from the dissecting knife is only the start of the Green Guerrillas campaign. Their leader is Tess Robertson, a genius at fighting environmental pollution and injustice - and equally brilliant at fighting with friends and family at the same time. Now Tess is planning her biggest battle yet. She has to stop a billion dollar paper mill from being set up in town, and pumping dioxin, one of the world's most toxic pollutants, into the air.