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.

In a dramatic showdown, humans and Synths go head-to-head - but will Mia and Max's peaceful protest cost them their lives? Laura, Niska and Mattie face major decisions.

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.

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.

Things are at the lowest possible ebb for the fractured Hawkins family. With Joe in exile and the kids tired of their parents' lies, Laura decides it's time to tell the truth

Laura discovers a shocking truth that threatens her life and those around her. Niska continues on her mysterious journey, and must defy all her instincts to survive.

As Leo struggles to come to terms with being human, Mattie takes him back to the Hawkins' home, where a surprise night out allows them to confront their feelings for each other. Laura is determined to uncover the truth about the too-secret Operation Basswood and tries to enlist Dr. Neil Sommer's help, only for things to take an unexpected turn. Joe reluctantly decides to help Karen with Sam, and Niska receives a mysterious message.

A grieving Max must face the consequences of his painful decision. Laura discovers she's not being told everything at the Dryden Commission, while Joe uncovers Karen's shocking secret.

The Hawkins, a loving but troubled family decide to buy a 'Synth' called Anita, but they start to suspect there's something unusual about her...

Athena travels to the UK and her tragic secret is revealed. Niska's consciousness assessments begin. With more time at home Joe notices Sophie's increasingly eccentric behaviour. As Karen returns to work with Pete, cracks start appearing in their relationship. The Synths are forced to leave their hideout but Mia shocks them with a huge decision.

When fractures within the Synth community start to appear, all hope of stability comes under threat, and both families are brought back to fight for the Green-Eyes' survival.

While Sam reels from the events of Waltringham and Joe struggles to help him through it, truths are revealed and dangerous plans put into action at the Railyard.

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.