The episode opens on the day of the rogue synthetic attack on Mars. It also happens to be First Contact Day, meaning most of the human staff is off-site. We see how the human skeleton crew treats the simple androids who work at the shipyards with them, specifically the unit designated F-8. F-8 looks like he's hacked before shutting down the shipyards' security systems. As ships attack the planet from above, F-8 shoots himself.
In the present day, Picard and the Romulans Zhaban and Laris investigate Dahj further. Dahj has been erased from the video feeds of the fight with the Romulans. It seems like something the Tal Shiar would do, but acting so brazenly on Earth is uncharacteristic of Tal Shiar operations. Instead, Laris and Zhaban suggest that it is another group called the Zhad Vash, an even more secretive organization that the Tal Shiar. They're believed to be a boogeyman-like myth by most Romulans. It is said that they keep a terrible secret and that they hate all forms of artificial intelligence.
Laris and Picard investigate Dahj's apartment. Laris can tell the apartment has been scrubbed by the Romulan agents. By examining Dahj's recent outgoing communications, she's able to discern that Dahj's sister is not on Earth.
Picard is visited by a medical officer whom he served with on the Stargazer. He comes bearing bad news. The abnormality in Picard's parietal lobe that Dr. Crusher warned him about in "All Good Things" is starting to become a problem. The doctor can't diagnose which specific condition it will become but they all end in death.
Picard heads to Starfleet headquarters for a meeting with the head of Starfleet, Admiral Yancy. There's some lingering animosity between them, but Picard explains the situation. Yancy doesn't believe Picard's story and denies his request for temporary reinstatement.
Dr. Jurati visits Picard at the château, at his request. She brings him everything she could find about Dr. Bruce Maddox that hadn't been boxed up and removed from his lab. Jurati also discovered there's no record of Dahj existing from more than a few years ago. She believes Dahj's entire existence was a "work of fiction" built whole-cloth about three years ago.
Laris is not happy with Picard's plan to go into space and search for Dahj's sister. Zhaban is more understanding but does tell Picard that he he'll need help. Picard has already contacted his old first officer, Raffi Musiker. They did not part on good terms and she's not happy to see Picard, but she can't help but be interested in what he has to say after he mentions that secret Romulan assassins are operating on Earth.
Soji and Narek have begun sleeping together, which Narek says they must keep a secret. The Borg cube they were at is "the artifact. It's dormant, separated from the Borg Collective hive mind. The Romulans have been profiting off of the tech they take from the artifact. The Romulans aren't sure how much of the cube is still functional. Soji works with the "X-Bs," former Borg that have been severed from the Borg collective and had their individuality restored. Some of them handle the transition better than others. The worse off ones suffer mental health issues. Soji seems more empathetic towards the X-Bs than her colleagues, especially the Romulans. They're unsure what species these drones were assimilated from and so refer to them as "Nameless."
Admiral Yancy contacts the head of Starfleet security, Commodore Oh, and tells her about Picard's visit to Starfleet HQ. Oh assures the admiral that there's nothing to worry about, but agrees to look into it. She summons Lt. Rizzo to her. Oh and Rizzo both know about these operations and Oh blames Rizzo for letting Picard know about them. Rizzo is now tasked with finding the one remaining android and she says she's put her best man on it.
Rizzo is actually a Romulan and her best man is Narek, her brother. She contacts him via hologram and tells him that she is returning to the Borg cube to oversee the operation. Narek is attempting to learn the location of a nest of other synthetics from Soji. If Narek's approach fails, Rizzo will try being more direct. She reminds him that both of their lives are at stake.