The Last Flight Of Dr. Ain by James Tiptree Jr.
This science fiction story revolves around the enigmatic Dr. Ain, who embarks on a global journey under the guise of a deadly pandemic. As he travels, his true intentions become clear: he aims to save the planet from the destructive impact of humanity by spreading a virus that targets humans specifically. Through a series of flashbacks and perspectives from those who encounter him, the narrative unfolds, revealing Dr. Ain's profound love for the Earth and his radical approach to conservation. The tale is a poignant exploration of environmentalism, ethics, and the extremes one might go to for the sake of the planet.