Sarah is deeply wounded and struggling to stay alive on the Island. Driven deep into its forest by Neolutionists and worse, she strives to make it far enough to rescue Cosima. Meanwhile, a recovering Cosima reunites with Delphine, but there’s way more going on this Island than Cosima imagined and Delphine can’t give her all the answers she needs. What is clear is that Rachel is now in firmly in charge at the right-hand of the 170-year-old founder of Neolution, PT Westmorland. Back home, Neolution puts the screws to Alison and Donnie in their hunt for Helena. The sestras couldn’t be further apart when they need most to be together.
Sarah works her way along the beach. She hears a sound, and is briefly attacked by a wild man. She fights him off and escapes.
Cosima awakes in a cabin in a village, still somewhat ill, and is met by a young woman named Mud, who introduces her to the village, called Revival; it has tents, huts, domes, livestock pens, storage barns, ATVs, and people. Mud describes it as a self-sufficient village, off the grid, and they are a project of P. T. Westmorland, people from every part of the world to improve the human race; he's 170 years old, and hopes to extend his longevity to everyone.
Alison and Donnie are hiding out, not at a hotel in Niagara, but with Helena in her hut in the forest. Felix calls them to say, stay put out there, Siobhan, Kira, and Sarah are missing, so stay safe. After he hangs up, Alison says let's go, we have to help.
Sarah, getting through the forest, finds that she is being tracked by men with rifles, from the village "Revival", and overhears that they have to get her back there with "the other one."
Delphine is running the Revival clinic, and is examining a little girl, a newcomer from Afghanistan named Aisha, who says she has cancer, and P. T. invited her here to get better. After she and her mother leave, Delphine hides Cosima's package with the Leda cure in the back of a refrigerator. Then The Messenger comes to say "he" wants her.
At the lair under the comic book store, Scott, Ira, and Hell Wizard are trying to locate Susan's house and the village; they've found satellite maps of the island, Ira was there with Susan and knows it, but the village he and Susan stayed away from.
Maddy Enger drives Art out into the countryside, and says they are going after Alison and Donnie, to lean on them for the whereabouts of Helena. She shows him a picture of Art's daughter, as a way of letting him know: Neolution will do anything to get Helena.
Helena and the Hendrix's in the forest see armed men searching, and it happens they run into Alison, bag and grab her. Donnie tries but can't bring himself to go rescue her.
The van with Alison meets Art and Maddy on a country road, and when Maddy asks about Donnie and Helena, she answers she has no idea. Maddy tries to impress upon Alison that the new Neolution is different, she's been ordered strictly not to harm any clone; but she then points her gun at Art and demands where Helena is. Alison splutters and says they are in the forest.
Charlotte and Cosima look at a book from the school at Revival; it is all about how they are chosen for a brighter future, where death and aging will not touch them. They agree Revival and its cult-like people are spooky. Delphine joins them briefly, and says the science here is real, the island is a decades-long longevity study, stem cell therapy and anything else that works. She remarks on young Aisha, she's just one of many children with cancer brought for experimental treatments. She gives Cosima the key to the medical clinic, and tells where the cure was stored. Then The Messenger is there to take her away, she's on a research trip to Sardinia for P. T.
Sarah falls asleep in the forest, and wakes to find a wolf, dead, next to her, killed by a spear. She gets away, and the men searching for her find the wolf, and their leader declares that it must be been a bear. The leader says the search is over, they go home.
At Revival, loudspeakers play a bit of the Tannhauser overture, and Mud gets Cosima to join the villagers as they assemble at the foot of the stairs to P. T.'s big house; that music is the signal for an announcement from P. T. Down the stairs, escorted by guards and The Messenger, is Rachel, who addresses the villagers on P. T.'s behalf. She announces that the fruits of 200 years of Neolution science are within their grasp, and those in the village will "drink from the fountain" first. All the villagers cheer. Sarah, peering in from the edge of the clearing, sees Rachel.
Donnie and Helena are still in the forest, and Donnie runs into a man with a gun. As the man attempts to take Donnie, Helena jumps him and subdues him, but along the way her belly gets punctured by a branch. Donnie gets her to the car to go to the hospital.
At night in Revival, Cosima sneaks to the clinic, and finds the cure safe, and also finds Sarah. Cosima doesn't want to get away, she's sure this village is the answer; Sarah should find the boat and get back home, but Cosima has work to do here. They hear the sounds of guards looking for Cosima, or maybe Sarah, and Sarah gets away, as Rachel enters. The cure is an injection into the uterus, and though Cosima had wanted Sarah to do it, Rachel does it for her.
Sarah gets to the boathouse, and there's a boat inside. Rachel and a guard come in; he shoots a dart at Sarah, and she falls unconscious.
- Tatiana Maslany as Sarah Manning/Cosima Niehaus/Alison Hendrix/Helena/Rachel Duncan
- Jordan Gavaris as Felix Dawkins
- Kevin Hanchard as Arthur Bell
- Kristian Bruun as Donnie Hendrix
- Ari Millen as Ira
- Josh Vokey as Scott Smith
- Maria Doyle Kennedy as Siobhan Sadler
Special Guest Star
- Skyler Wexler as Kira
- Kathryn Alexandre as Tatiana Maslany's Acting Double
- Ron Lea as Detective Hardcastle
- Jenessa Grant as Mud
- Elyse Levesque as Detective Enger
- Geza Kovacs as The Messenger
- Andrew Moodie as Mr. Frontenac
- Cynthia Galant as Charlotte
- Calwyn Shurgold as Hell Wizard
- Stuart Hughes as Cooper
- Victor Gomez as Salvador
- Sirena Gulamgaus as Aisha
- Homa Kameh as Aisha's Mother
- Vas Saranga as Amar
- Andrew Musselman as The Creature
- Calvin Desautels as Neo Agent #1
- Bobby Brown as Neo Agent #3
- John Nelles as Dialogue Coach
- "Overture: Tannhäuser" by Royal Philharmonic Orchestra