The famous detective Shiro Tachi, who aims to be the world's number one detective, is in town and comes to Mackenzie to challenge her. Penelope turns up during their meeting and claims that her bananas have been stolen, and Tachi declares that the one to solve the case first will win their challenge. Mackenize investigates and discovers that there are no bananas left in the town, but gets a lead that the culprit might be hiding deep in the forest. Tachi's pet, Goldie, collapses, unbeknown to Tachi. Mackenize hunts down a doctor, who tells Mackenize that Goldie has a cold, something which is potentially fatal for an animal like her. Mackenize tries telling Tachi about Goldie's condition, but he doesn't pay it any mind until he is told that could kill her. Tachi entrusts the case's resolution to Mackenzie to be by Goldie's side. Mackenize and Inspector Daria discover the Cornstalker's hideout in the forest, where he is planning to use the stolen bananas to make a sentient "Banana Man". He is being aided by a scientist, who is the brother of the doctor. Mackenzie is able swap some of the bananas with spoiled ones, which causes Banana Man to be born improperly, thus stopping the cornstalker's plot.