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.

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...