Trama

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.

Fearing retaliation from Species 10-C, Rillak moves up the time-line for first contact. Kovich says that there is no precedence for how this first contact will go. The mere presence of the Discovery might be taken as an act of aggression. Plus, the Federation destroyed the DMA. There are no translators that would work in this situation. Dr Hirai (Hiro Kanagawa) is a Astro-Linguist assigned by Kovich to help with this mission.

Rillak, T'Rina, and several diplomats board Discovery, which jumps to the galactic barrier and begins the dangerous flight through it. Rillak joins the mission as she was the Federation's top ambassador for 20 years and she knows that her skills will be needed.

The DMA controller is the same size but significantly more powerful that the one destroyed by Book and Tarka. It is churning through space at a much faster pace. It will process the current sector in 12 hours before jumping. Tarka and Book also decide to travel to the hyper-field coordinates. But the Mycelial network ends at the galactic barrier and the barrier itself is made of anti-matter which will eat through the ship's fields. Tarka says that Book needs programmable anti-matter to get through the barrier. Tarka says that the anti-matter will have to be applied to the ship's hull and it will repel the negative energy of the galactic barrier.

Discovery knows that they will lose communications with the Federation as they enter the galactic barrier. Saru asks T'Rina if she wants something more than a friendship, but she avoids the question. Burnham and Rillak agree that the ship will be Burnham's authority, but all the diplomats and the first contact will be handled by Rillak.

Before they lose contact with the Federation, the Discovery are contacted by Vance, who tells them that the DMA is now close to destroying Earth and Ni'Var. The Discovery has 71 hours to complete its mission. Stamets figures out a way through the barrier riding a vacuum state fluctuation that form discrete bubbles inside the barrier. The bubbles are protected space that pass through the barrier at random intervals.

Meanwhile, Book and Tarka travel to a stash of it that Tarka has in an abandoned prison of the Emarald Chain where he was once held. Tarka explains that he had befriended a fellow prisoner, Oros (Osric Chau), who built a machine to transport them to a peaceful parallel universe. Osyraa (Janet Kidder), the leader of the Emarald Chain wanted Oros and Tarka to build her an alternate engine that does not require Dilithium.

It took over a year, but Oros and Tarka became good friends and companions in captivity. Oros talks about a parallel Universe that is at peace and reveals that he has built a machine to get himself transported there. He planned to use the Geo-Thermal energy of the prison planet and the warp core that they were building as energy sources.

The machine doesn't work as it needs more energy. Unknown to Oros, Tarka had betrayed him to Osyraa. Tarka has a change of heart and tries to save Oros when the guards attack, but Oros is too injured. Oros forgives Tarka and asks him to leave and save himself. Oros and Tarka were separated and Tarka does not know if Oros was successful to get to the parallel Universe. Tarka hopes so and has built his own machine so that he can also travel there. The machine requires a large amount of power, and Tarka had planned to use the DMA's power source before realizing that it is at 10-C's location rather than in the DMA itself.

After a difficult flight, Discovery emerges from the galactic barrier and begins traveling towards 10-C's coordinates.