When communication with Cosima is cut off and Neolution appears to be within striking distance, Sarah’s alliance with Rachel goes out the window. Sarah lures a high-level Neolutionist into a trap, and sets out to bring down Neolution once and for all.
In a scene we've seen before from the Season Three finale, Delphine gets out of her car in the Dyad parking floor. Now we also see Krystal, hiding behind a car and watching. Delphine realizes she is being followed, turns, and this time we see, it's Martin Duko, pointing a gun at her. She asks "What will happen to her?" There is a gunshot and she falls. Duko aims to shoot again, and is surprised by the sound of a phone ringing nearby: it's Krystal's phone. Duko moves towards the car Krystal is behind, and then another car arrives from the other direction. Duko puts away his gun and leaves. Krystal runs to Delphine, who is groaning, and a van comes to them. Dr. Van Lier and some helpers get out; Van Lier takes over the medical assessment of Delphine; they stabilize her and rush her off to a waiting helicopter.
Delphine has fuzzy images of being transported, of doctors working on her, more transport. Then her vision settles in a bedroom, in a cabin, with a man looking at her, the white-bearded man that Rachel has been seeing visions of.
At Susan's island, she and Cosima agree that the fertilized egg is developing well. Susan leaves the lab for a moment, as Cosima calls Sarah via Skype to report: the cure is definitely under way. Suddenly Cosima's display shows "Access Denied", and it looks like she has a computer problem. Then the Skype session freezes also, for both parties.
Krystal is talking with a friend at a cafe, and they see news reports of Evie Cho's disastrous press conference and its aftermath. They agree this is part of the big beauty industry's corruption. The news shows Dr. Van Lier making a speech as acting CEO of BrightBorn, and Krystal calls Felix to tell him, Van Lier was the doctor who came to treat Delphine when she was shot.
At Rachel's hotel, Ira can't get in touch with Susan, and they plan a helicopter to get them back to the island. Sarah calls, and she and Rachel have had the same communications problem with the island. Rachel seems oddly calm and explains that reception to the island can get spotty sometimes. It doesn't seem like a random failure. It's more like, once Cosima finished the work, Susan cut the house off from the rest of the world.
Felix tells Sarah what he heard from Krystal. They figure that there are two competing factions in Neolution, bots(Evie Cho) vs clones(the Duncans), and they don't want to be caught in the middle of their feud.
Neolution is having a board meeting, and board members are grilling Evie Cho over the problems at BrightBorn. She tries to turn the discussion to the future that she could create, but her time is over; Van Lier touches something to her cheek (she had a bot there, too), and she collapses. Van Lier remarks, "technology is subject to natural selection too", as she dies.
Ferdinand comes to Rachel at her hotel. After a bit of argument about dealing with the Neolution intrigue, they restart their rather violent sexual play, with him accepting her domination. Ira has important news- but walks in on them and sees Ferdinand tied to the bed and Rachel on top-Susan is about to call them. Ira expresses that he needs to get ready for tomorrow, though Ferdinand gently takes him by the shoulder and tells him he won’t be needed anymore.
Krystal comes to the lair under the comic store, and although Felix thinks it would be better if she didn't know, she is introduced to Sarah as her clone, though Krystal is not convinced (according to her, her tits are way bigger then Sarah’s, has prettier hair and is overall is much more attractive person then messy, punky Sarah) and she and Art explain the situation to her, which she as usual garbles: to her, there are two factions, Estee Lauder, and a Swedish cosmetics company called Neolution, and they both are making trouble to beauty professionals.
Cosima is walking around in the lab underneath Susan's house, and overhears the conversation as Susan calls Rachel; Susan says they are testing the cure, and are now able to restart the human cloning project. The Neolution board has replaced Evie with Susan, and she will be back in Toronto tomorrow. After she hangs up, Cosima comes in and says that, to Susan, the clones are just lab rats. Susan says that this is just how Neolition operates, it said so right there in the book, which just so happens to have been written this this very room. Cosima is a bit taken back by this random piece of trivial, but Susan can‘t have Cosima interfering, and leaves the room; it's the bedroom Rachel was stuck in earlier, and now Susan locks Cosima in.
Outside the BrightBorn offices, an impromptu news conference seems to be happening, with Dr. Van Lier answering some questions from reporters. Krystal comes up to Van Lier and starts harassing him by yelling st him to ‘explain all about the dead babies‘, which wips the other reporters into a frenzy as they pile on. He recognizes her and gets fustrated that she’s getting involved, but if it‘ll Calm her down, he’ll talk with her privately. She leads him to a truck, where Krystal takes off her sunglasses, and her accent changes also: she's Sarah, and Van Lier recognizes her. He says he had nothing to do with shooting Delphine, that was Evie's doing, and he had contrary orders from the Neolution board to save her. But now, Susan may be out of the picture, and Rachel has convened the Neolution board without Susan.
Rachel enters the Neolution board room, and announces that human cloning is now back on as a Neolution goal. They are a little skeptical, but Rachel convinces them that she is more effective than Evie was. The clones are patented lab animals, with no legal or moral rights, and can now be made reliable for generations, so we will use Susan's cloning technology merged with Evie's implanted bots. The board is impressed with Rachel's determination to use the clones as mere tools.
Sarah, Felix and Art arrive in Rachel’s hotel room and see Ira chained to the bed(“wrong bitch-boy”, as Felix says) and they assess the situation, and figure that Rachel is headed back to the island to take control. (Indeed, we see Rachel in the helicopter, landing there.) Sarah makes preparations to follow her to the island. Felix convinces Ira that Rachel is now their enemy and Susan is in danger. He needs to use his phone to call and warn Susan what Rachel is doing.
Rachel gets to Susan's house, and finds the white-bearded man, who Susan introduces as "a messenger". Despite Rachel's attempt to take over, Susan says clones are property, and "they" won't really accept her.
In Susan's basement, the door to Cosima's room opens, and Charlotte says that Rachel is back and making trouble, so Susan recommends Cosima and Charlotte get to the boat. Charlotte mentions that there are other people on the island, but "we" aren't supposed to go there. Cosima takes the package with the cure in it with her.
Rachel is still arguing with Susan, and Rachel says she's ready to make the hard choices that Neolution raised her to do. But Susan controls the cure, and isn't really controlled by the board, and won't allow Rachel control of the clone process. Susan admits that after meeting with the other clones, like a Cosima and Sarah, shes ashamed of Rachel and regrets even creating her.Rachel grabs a knife from the kitchen and stabs Susan in the stomach.
Sarah arrives by helicopter, and goes to Susan's house. She follows a blood trail down to the basement, where Susan, covered in blood, is trying to do first aid. Then Rachel is there behind Sarah, and they fight, Rachel eventually stabbing Sarah in the leg. Sarah gets away, and limps into the forest.
Cosima and Charlotte wander in the forest, Cosima's physical condition deteriorating in the cold; they are met by the white-bearded man, The Messenger, who leads them to a well-lit, well-populated village. A cabin opens and Delphine comes out. They get Cosima into bed, and Delphine warms her.
Rachel completes bandaging Susan, and talks about the visions she's had, she's seen the swan, The Messenger, the village. Susan says it's a sign that "he", who built her eye, is getting capricious in his old age, the man behind the curtain, who wrote the book on Neolution over a century ago.
Cosima is half-conscious as Delphine is explaining to The Messenger that she had to treat Cosima. The Messenger is concerned that "he" isn't happy about it, and she won't be allowed to stay with her. After he leaves, Delphine tells Cosima they need to be careful here.
Sarah calls up Mrs. S’ phone to tell her what happened, but Ferdinand picks up and reassures her that her family is just fine he says as he points a gun at Mrs. S and Kira inside the safe house.
Rachel does a video conference from Susan's house to Dr. Van Lier and the Neolution board. She assures them that "the science is secure". They thank her, and say "Mr. Westmorland will see you now." Rachel is standing outside a wooden building as the door opens and she smiles.
- Tatiana Maslany as Sarah Manning/Cosima Niehaus/Alison Hendrix/Helena/Rachel Duncan/Krystal Goderitch
- Jordan Gavaris as Felix Dawkins
- Kevin Hanchard as Arthur Bell
- Ari Millen as Ira
- Josh Vokey as Scott Smith
- Kristian Bruun as Donnie Hendrix
- Maria Doyle Kennedy as Siobhan Sadler
Special Guest Star
- Jessalyn Wanlim as Evie Cho
- Lauren Hammersley as Adele
- Rosemary Dunsmore as Susan Duncan
- Cynthia Galant as Charlotte Bowles
- James Frain as Ferdinand Chevalier
- Gord Rand as Detective Martin Duko
- Scott Wentworth as Dr. Ian Van Lier
- Lucie Guest as Zoie
- Calwyn Shurgold as Hell Wizard
- Géza Kovács as The Messenger
- Frank Moore as Board Member #1
- Andrea Davis as Board Member #2
- David Christo as Reporter #2
Sneak Peaks and Promos
- For her "camp" look, Evelyne Brochu went almost completely without makeup for Episodes 4.09: The Mitigation of Competition and 4.10: From Dancing Mice to Psychopaths. Producers also thought it was time to bring back some of her infamous curls, for practical and realistic reasons and for the Cophine fans.