The Archangel was called to the planet Acheon. The indigenous people, while negotiating with Federation diplomats were placed under siege by a small group of worlds called the Zetarian Empire. After a rescue effort by the crew the Diplomats and Acheons were freed. It was then revealed that the entire mission was a test. An illusion created by the Acheons to see if humanity has moved past violence. While we have not our species was said to have "potential".