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.

Mia and Ed get closer but their relationship is thrown into jeopardy when their secret is discovered. Toby gets closer to Renie but offends her when he breaks through her synthie mask. Things look bleak for Niska until Laura brings in a surprise witness. When Milo confronts Athena about her secret agenda, she persuades him her research could be mutually beneficial. Karen and Pete delve deeper into the mysterious 'seraphim' investigation. As Hester's influence over Leo becomes clear, cracks appear between him and Max.