Killer Synth is the breaking news story, and public panic is growing. Karen is hot on Niska's tail, but are her motives for finding her more personal than professional?

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

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?