After receiving a message from Book, Burnham and Georgiou embark on a rogue mission to find him, leaving Saru to pick up the pieces with Admiral Vance. Meanwhile, Stamets forms an unexpected bond with Adira.

Discovery ventures to the Verubin Nebula, where Burnham, Saru, and Culber make a shocking realization about the origin of the Burn. The rest of the crew faces an unexpected threat.

Saru returns to help the U.S.S. Discovery uncover the mystery of an unusually destructive new force. As Burnham leads the crew, she must also find a way to help Book cope with an unimaginable loss.

Seeking answers, the U.S.S. Discovery ventures into a subspace rift created by the Dark Matter Anomaly. Meanwhile, Book faces a strange visitor from his past.

Captain Burnham and her crew must go where few have gone before: beyond the Galactic Barrier. Meanwhile, Book learns the truth of what drives Ruon Tarka.