A former astronaut helps a government agent and a police detective track the source of mysterious alien pod spores, filled with lethal flesh-dissolving acid, to a South American coffee plantation controlled by alien pod clones.

Bud Spencer plays Banana Joe, a brawny yet friendly man who lives in a small rainforest village called Amantido with a huge number of his own children and regularly delivers bananas to a South American river port (hence his name). One day, the henchmen of a local gangster boss named Torsillo come ashore in Amantido to initiate the construction a banana processing plant. Of course, Joe (in typical direct-approach manner) evicts the goons, who promptly return to their boss. Torsillo finds out that Joe is trading bananas without a license and decides to exploit it. Upon his next delivery, Joe is apprehended by the police and given the choice of either acquiring a legal license or getting his boat taken away and himself arrested for illegal shipment. Joe travels to the nearest city, which to him is a new world, as he grew up in the rainforest.

The simple story has the pair coming to the rescue of peace-loving Mormons when land-hungry Major Harriman sends his bullies to harass them into giving up their fertile valley. Trinity and Bambino manage to save the Mormons and send the bad guys packing with slapstick humor instead of excessive violence, saving the day.