That's Why I Have to Go

Synopsis

On the Orion, Chako determines that virus-like nanomachines have entered Adam's body and changed the nanomachines already there into malignant ones, and they probably entered through the scrape on his hand. They decide to head directly for the nearest sub-terraforming machine. After passing through a forest, they reach an ancient, crumbling city. They stop by a large building that they hope is a hospital, but the medicines they find had already decomposed long ago. Chako estimates them to be five hundred to a thousand years old, the same age as Adam's ruins. When Howard finds writing on a medicine bottle that's the same as writing they saw in the ruins, they realize that Adam's people had come from this planet, which raises the question of why he was in a spaceship on the island. They continue on to the terraforming machine, but are prevented from approaching by a spherical drone that fires a laser at them. Luna wants to approach alone, hoping that the nanomachines in her body – along with Adam's ID card – will cause it to recognize her as one of Adam's people, but the rest of the children insist on acting as decoys. When Luna addresses the drone, it briefly glows blue, and she hears a voice saying "people are unnecessary". The drone vaporizes Adam's ID card, and is about to attack Luna when Bell rescues her. Kaoru leaps on the drone and stabs in with a knife, destroying it, but in the process the drone's laser shatters the entrance door on the terraforming machine. Luna tells the others about the voice she heard. (Source: Wikipedia)