Laura is begrudgingly forced to keep Anita when she saves Toby from a road accident. George is planning an escape with Odi and Pete's hot temper earns him a suspension from work.

Laura insists the family take Anita for testing when Mattie tells her that she's seen Anita acting strangely, while Hobb is on Niska's trail.

Rejected and alone, Karen sets out to George's house to find Niska. Meanwhile Pete is determined to find out who Karen really is. The hunted Synths take refuge at the Hawkins.

With the Synths in captivity, the devastated Hawkins' realise how much Mia and her family mean to them and are determined to help them.

The Hawkins family try to get their lives back on track. Niska is driven to a fateful decision while on the run in Berlin. Leo, Max and Mia are living in hiding near a coastal town when they are threatened by a mysterious organization.

Laura must decide whether to accept Niska's request, while Karen and Pete learn about a special Synth being sold for unprecedented amounts on the black market. Hester uses questionable means to gain information from her prisoner, and Leo faces a new mission. Mia takes a risk to help Ed but is her secret now in jeopardy?

When Mia risks falling into the hands of a mysterious organisation, she is forced to take drastic action. Odi struggles to find meaning, while Sophie is awestruck by Renie's 'Synthie' lifestyle. As Pete recovers from his assault, Karen makes an admission that rocks their relationship. Hester and Leo stake out the Silo and track down the sniper who killed Ten. Hester agrees to deal with her peacefully, but can she be trusted? Mattie leaves home to reconnect with Leo.

Athena challenges Milo's ethics and is shocked when he reveals his real plan. Mia's surprise return has ramifications for the Hawkins family. Mattie finds Leo but can she trust him with her secret? Max resolves to begin a new community of Synths; when he learns how far Leo is prepared to go to complete his mission, he takes matters into his own hands.