In the village of Trion, a gorilla soldier sees a human and goes into
convulsions, and collapses next to a pond.
The guys are leaving the home of Talbert and his daughter Amy but after they're gone, Talbert collapses complaining of fatigue and temperature.
Nearby, Urko receives a report of "sleeping sickness" from the village and goes there.
At the guy's camp that night, Galen is worried and upset that Alan shared information about them with Amy – she was in love with him and he tried to explain how he was married in the past, but she didn't believe him.
The Ape Council is preparing to eliminate the village but the chief medical officer, Zoran, believes he can produce a cure and wants to use the village as a laboratory. Over Urko's objections, the Council agrees.
The guys run into a coal carrier who escaped the quarantine and warns them of the danger. Alan insists on going back, suspecting they may have caused the disease. Pete agrees--Galen is upset they're putting the team at risk but goes along. When the gorillas turn them back, they sneak in via another route. They find the first man near the stagnant pond and notice the mosquitoes, then get into Trion and meet Amy--Talbert is dead.
Alan tries to rally the villagers but Zoran arrives and has his own bizarre treatments involving bleeding and bathing. Galen pleads their case and they try to explain about the mosquitoes and "malaria." Zoran doesn't believe them and prepares to have them shot. However, one of the gorillas collapses with malaria and dies, disproving Zoran's bodily-contact theory. Left without an explanation, Zoran is shocked.
The Ape Council arrives and Urko closes down the village entirely, preparing to burn it down. Zoran presents the astronaut's theory as his own and gets laughs from the Council. Zaius is willing to risk the entire village to get an ape cure and gives Zoran the go-ahead. Zoran returns to the village and tells the trio how he took credit for their theory and protected them from Urko so he doesn't lose his source of knowledge. They tell Zoran they need a tree with quinine to make a cure, while sending villagers in protective masks to smoke out the mosquitoes and drain the ponds.
Urko arrives but the guys put on their masks to conceal themselves, further raising Zoran's suspicions. As Alan and Pete find the proper tree and bring the bark back, Amy collapses of malaria. They begin administering the medicine to the sick villagers as a delirious Amy rambles about Alan's story and Zoran overhears. He's interrupted by another gorilla, Kava, collapsing, and an angry Urko insists they destroy Trion. Zoran makes a desperate plea for a few more hours and Zaius breaks the deadlock, giving Zoran until noon the next day.
The cure isn't working as fast as Alan thought, due to the potential variables, but he preaches patience. After he leaves, Zoran tries to get more info on Alan from the delirious Amy and she mumbles more of what he told her. Galen interrupts him before she can confirm that Alan's an astronaut and tries to cover for her delirium. Meanwhile, Alan spots the ailing gorilla nearby--touched by his plight, he sneaks into the camp to give him some of the quinine extract. Another soldier spots him and he is forced to flee, leaving the medicine behind. Urko checks it out but Kava isn't in any condition to identify anyone.
Urko rides in early and Zoran swears he'll claim the victory for himself. He confronts Urko and Zaius backs him up. But Alan rallies the villagers, now cured, to come out and prove the cure works. Kava also stumbles into the camp, confirming that it's no trick, and Urko has no choice but to withdraw.
Later, Zoran insists he must turn them over to Zaius as he's figured out who they are. They call his bluff, pointing out Galen can convince Zaius that Zoran didn't have the cure. Galen stands with his friends, much to Zoran's astonishment, and he has no choice but to let them go rather then admit they were helping him. Alan bids farewell to Amy and leaves her to her own future, then the trio departs.
Written by Gadfly on Nov 28, 2016