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...

Laura feels increasingly threatened by Anita's presence, and Leo's quest for information takes him to dangerous places.

Laura is begrudgingly forced to keep Anita when she saves Toby from a road accident. George plans an escape with Odi. 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. Hobb is on Niska's trail.

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.

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' home.

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