News of the `Killer Synth' finds its way into the media, causing widespread panic, and placing Karen under even more pressure to track down the alluring fugitive Niska. However, it seems there may be an ulterior motive to her hunt for the murderous synth. Meanwhile, the Hawkins debate whether to keep Anita in light of their recent discovery that she is not quite as `new' as she seemed, and while Joe worries his domestic synth might inadvertently reveal his secret, Mattie's decision to place her trust in Leo could put an end to the family's arguments.

The episode was rated 7.74 from 2493 votes.

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?

The episode was rated 7.74 from 2747 votes.

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.

The episode was rated 7.76 from 2453 votes.

Mia and Ed get closer but their relationship is thrown into jeopardy when their secret is discovered. Toby gets closer to Renie but offends her when he breaks through her synthie mask. Things look bleak for Niska until Laura brings in a surprise witness. When Milo confronts Athena about her secret agenda, she persuades him her research could be mutually beneficial. Karen and Pete delve deeper into the mysterious 'seraphim' investigation. As Hester's influence over Leo becomes clear, cracks appear between him and Max.

The episode was rated 7.80 from 2458 votes.

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.

The episode was rated 7.82 from 2347 votes.

Laura leads a tense Dryden Commission on a visit to the Railyard, but will Agnes' anger threaten its success? Mia comes face to face with Ed forcing her to confront her past, while an evening out for Karen, Sam and Joe turns to tragedy.

The episode was rated 7.83 from 958 votes.

Laura feels vindicated when Mattie tells her that she has seen Anita acting strangely. Laura insists that the family take Anita for testing and they're shocked to discover she's 14 years old. After meeting Leo through the Headcracker forum, Mattie thinks she might have an idea. Pete becomes stir crazy, stuck in the house with Simon.

The episode was rated 7.89 from 2568 votes.

Max must confront a friend turned foe. Laura reels from her heartbreaking decision, but when Mattie reveals her secret, she is spurred back into action. Niska's journey takes an unexpected turn, while Leo races to be by Max's side, but walks into danger.

The episode was rated 7.91 from 877 votes.

The fractured Hawkins family reaches its lowest ebb, with dad Joe in exile, and Mattie, Toby and Sophie tired of their parents' lies. As the situation reaches breaking point, Laura decides it is time to tell the truth, and her confessions has incredible consequences for household synth Anita. Meanwhile, Karen finally discovers `killer synth' Niska's whereabouts, and a joyful reunion for the runaways is cut tragically short when a brutal betrayal forces one of their number to make the ultimate sacrifice.

The episode was rated 7.92 from 2430 votes.

Stanley and Anatole's true colours put Laura and her family directly in harm's way. With Mia speaking at the commission, Laura must do everything in her power to stop an awful attack. Leo and Mattie return to the Elster house where Leo comes to understand a painful truth, but Mattie has a secret that could knock their fledging relationship off course. Niska continues her mysterious journey that takes her to Wales, where she must defy all her instincts to survive.

The episode was rated 7.93 from 898 votes.

With the Synths now in captivity, Hobb attempts to extract Elster’s consciousness programming from their brains. There ends up being one final piece of the puzzle missing that nobody, including Leo could ever have imagined though. The devastated Hawkins family come to realise much Mia mean to them and their courage is put to the test as they take on Hobb and his forces in an effort to save the Synths from their imprisonment.

The episode was rated 7.96 from 2390 votes.

Rejected and alone, Karen sets out to George's house in search of Niska. Meanwhile, Pete is determined to find out who Karen really is, but his enquiries reveal a truth stranger than he could ever have imagined. The hunted synths gather at the Hawkins, grateful to Laura and family for providing refuge. As humans and synths live alongside each other in peace, could this be the harmonious future that Leo and co have longed for? But as Hobb gets closer, it may be too late for them to find out.

The episode was rated 8.00 from 2403 votes.

When Mattie reveals that the Synths are planning to break into the Silo, Laura is determined to find Niska and ask for her help. Mattie asks Max to help save Leo from Hester's influence. Toby receives a disturbing message from Renie. Karen seeks out Athena's expertise and makes a life-altering decision. Mia and Hester break into the Silo, but things don't go according to plan.

The episode was rated 8.01 from 2314 votes.

In a dramatic showdown, Mia, Max and the synths go into battle with humans; Laura, Niska and Mattie face monumental and life-changing decisions.

The episode was rated 8.17 from 850 votes.

The acclaimed drama concludes. In the aftermath of the Silo tragedy Karen feels she and Sam have no future and takes matters into her own hands. Niska and Astrid prepare to return to Berlin, but can Niska really walk away from her family? Joe leaves Laura shell-shocked with a frank admission. Hester seeks revenge and will stop at nothing to hurt Leo.

The episode was rated 8.19 from 2229 votes.