Saru becomes captain and Discovery travels to Earth, which has left the Federation, and the crew brokers peace between Earth and raiders from Titan.
Reunited with the crew after her year with Book, Burnham hears of a message from Admiral Senna Tal, and Saru is formally named captain with Burnham as his first officer. Discovery jumps to Earth, which has left the Federation and guards itself with a defense force, and learns that Tal is dead.
When raiders attack, Burnham and Book capture their leader Wen, who reveals that his people are humans from Titan cut off from Earth's resources. The crew helps negotiate an agreement between Wen and Earth's Captain Ndoye. A young human named Adira is found to be the host of Tal's Trill symbiont. Jonathan Frakes directed.