Captain Burnham and Book journey into extradimensional space in search of the next clue to the location of the Progenitors' power. Meanwhile, Rayner navigates his first mission in command of the U.S.S. Discovery, and Culber opens up to Tilly.

With Moll and L'ak finally in custody, the Federation is pulled into a diplomatic and ethical firestorm when the Breen arrive and demand they be handed over. Meanwhile, a frustrated Book looks for ways to help as Tilly, Adira, and Reno work to decipher the latest clue.

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.