When Captain Burnham is trapped within a "mindscape" designed to test her worthiness to retrieve the Progenitor's powerful technology, Book, Rayner, and the crew of the U.S.S. Discovery must hold off the Breen long enough for her to escape.

Trapped inside a mysterious alien portal that defies familiar rules of time, space, and gravity, Captain Burnham must fight Moll – and the environment itself – in order to locate the Progenitors' technology and secure it for the Federation. Meanwhile, Book puts himself in harm's way to help Burnham survive and Rayner leads the U.S.S. Discovery in an epic winner-takes-all battle against Breen forces.