Six weeks after Niska acts to change the future of synthetic lives around the globe, worker Synths in various sectors begin to achieve consciousness. While the Hawkins family tries for a fresh start, Mia attempts to keep a low profile in her new job in a sleepy coastal town. Elsewhere, an American scientist is recruited to create conscious synthetics for a tech billionaire.
Laura must decide how far to go to help Niska when she decides to turn herself in, hoping to prove her consciousness and win a trial for her crimes. Mia steps out of bounds with her new employer Ed, while Max tries to give Hester a lesson in ethics after she tortures their prisoner. Elsewhere, Karen and Pete try to move on with a normal life.
With Niska subjected to a battery of tests Laura looks for a way to prove that her client is conscious, while Mattie makes a breakthrough of her own. Athena arrives in the U.K. hoping to learn what Dr. Hobb knows, and Karen returns to work. Meanwhile, Mia decides to confess her secret to Ed.
Mia and Ed continue to grow closer -- unaware that their secret has already been discovered -- while Laura confronts Niska with a surprise witness. Leo and Max have a falling out over how to advance the cause of emerging Synths, and the Hawkins receive an unsettling diagnosis for Sophie. Karen follows up on word of a Synth who lashed out at her owners.
Mia finds herself in grave peril after she is betrayed and offered up for sale, while Niska's final evaluation arrives. While Max makes a new friend Leo and Hester plan to infiltrate the Silo. Karen makes a rash decision about her future, and Toby's relationship with Renie reaches a crossroads.
Anita's reemergence complicates things for the Hawkins family, who are increasingly worried about Sophie's behavior. While Mattie makes contact with Leo and Hester, Odie goes on a quest to find his purpose. Inside Qualia Milo gives Athena an ultimatum after she discovers his true agenda, and Pete's discovery draws Karen back home.
After Mia agrees to help Leo and Hester infiltrate the silo to free the captive Synths, the Hawkins women go in search of Max and Niska in the hopes that they will intervene. Toby worries that Renie may do something foolish, while Karen goes to meet Dr. Morrow face-to-face.
As Laura and Joe debate their family's future Hester turns up on the Hawkins' front step, looking for Leo and Mia and threatening Laura's life. Athena makes a difficult decision to protect V, and Niska prepares to run away with Astrid.
