Sarah regresses to old habits while struggling to cope with the consequences of her decisions —reconnecting with Beth on a dark night of the soul. Back at the lab, Cosima, haunted by vicious memories and news of Delphine, attempts a dangerous Hail Mary to find a cure. At the Hendrixes, Alison is more determined than ever to create normalcy for her kids. As she forges ahead with a birthday party, Donnie is caught in the Neolution crosshairs.

As P. T. Westmorland demands a more aggressive action on Kira, and Sarah fights to save her daughter, Rachel discovers a dark secret that makes her question her place within Neolution. Meanwhile, Cosima has returned with a vital clue to Westmorland's true identity.