In 1974, biologist Philip Carvel makes the acquaintance of a young well-connected woman in the British government. She's the first one to take his warnings seriously about how the planet can't sustain humanity's growing numbers, and the two of them put into action a plan that will render 95% of the world's population sterile.
The Network tortures Jessica for the nature of the adjustment that her father made to Janus. Meanwhile, Ian and Grant try to find Becky, and Arby tries to make a new life for himself but receives a visitor from his past.
Arby takes Ian, Becky, Grant, Donaldson, and Anton into hiding, and they soon work out who Anton really is. They go to a teenager hacker, Ben, who confirms what the Network has planned. Meanwhile, Lee and Wilson work together to track down the fugitives, while Michael is forced to betray a new friend to protect the Network's secrets.
Dugdale reluctantly agrees to harbour Jessica and after he visits Jen and Alice in a secret prison it's clear he will do whatever The Network asks in order to keep his family safe. Jessica is looking for Ian, as is Milner who believes that he will lead her to Carvel.
After the revelation that her father is alive, Jessica, is determined to find him, with hostage Milner in tow. Arby has takes Anton and Grant to a remote place from his past. Ian and Becky want to tell The Network that Janus is racially selective, so that they can try and stop the flu virus from being released.