It is the start of a new age and Bonk has returned at the turn of the tide as the world faces extinction. Our loveable caveman is back and has brought his huge head with him. A doomsday comet, surrounded by smaller chunks of debris, is on a collision course with Earth. A strange magnetic field around the comet seems to be driving most of the planet's weak-willed creatures crazy, and smaller bits of debris are smashing into the jungle near Bonk's home. Bonk must undertake a perilous journey that will take him to the very center of the planet to save the world.