Burnham and the Discovery crew travel to Book's home planet to help rescue it from Osyraa, the formidable leader of the Emerald Chain. Stamets and Adira continue their search for valuable information about the origin of the Burn.
Set roughly ten years before the events of the original Star Trek, the series follows the crew of the USS Discovery as they discover new worlds and civilizations, while exploring the franchise's signature contemporary themes. The season-long story line revolves around an incident and an event in Star Trek history that's been talked about but never been explored.
Star Trek: Discovery - The Sanctuary Synopsis and Schedule