Unification III is a direct follow up to two previous episodes of The Next Generation: Unification I & Unification II from TNG Season 5. In the two-part story, Jean-Luc Picard and Data travel to Romulus undercover after Ambassador Spock (Leonard Nimoy) has been spotted there unauthorized. Spock tells Picard and Data that he is trying to reunite the Vulcans and Romulans. Ultimately, Spock stays behind on Romulus to help work toward true reunification by trying to change society from within, no matter how long it takes.
Star Trek Discovery Season 3 Episode 7 takes place 820 years after Unification 1 & 2. After being demoted and losing her title as First Officer, Michael Burnham (Sonequa Martin-Green) is unsure how she fits in with Starfleet, while getting closer to Book. But above all, she wants to solve the mystery of The Burn. Each of the three black boxes they have recovered lost contact at different times, within a difference of millionth of a microseconds. Burnham finds an experiment called SB-19, which spread sensors across dozens of lightyears of subspace. But its findings were not made public.
The SB-19 data belongs to the planet Ni'Var, formerly Vulcan. The Vulcans now share the planet with the Romulans. Centuries after Spock's death, his mission of unification was successful. However, Ni'Var left the Federation nearly 100 years ago and kept the SB-19 data secret. Admiral Vance chooses to leverage Michael Burnham's relationship to Spock in order to reopen conversations with Ni'Var to request the SB-19 data. This also results in an unexpected reunion for Michael. Meanwhile, Saru asks Tilly to be his acting First Officer.
Chastity and Greg recap the story and comb through Episode 7 for Easter eggs and Star Trek references from Star Trek (2009), past episodes of TOS, TNG (Unification I & Unification II), and Star Trek: Picard.