Cosima takes a turn for the worst, forcing Sarah to take desperate action — with tragic consequences for those she loves. The Proletheans set their ultimate plan into motion. Alison and Donnie tangle with the law.
Alison and Donnie wrap Dr. Leekie's body in plastic, and store it in their freezer. It's hard to get Donnie going, he's aghast and disgusted by it all, but Alison is pushing, getting through it (like she got through cleaning Felix's apartment).
At the Johanssen's farm, Henrik implants the embryo he has prepared into Helena's cervix, ready for it to implant in her uterus. She is not looking particularly eager, but is at least accepting and calm about it. She gets a new room in the compound, and clothes. They show her the farm's nursery and preschool, and Helena is welcome there at any time.
Delphine reports to Rachel that Cosima's growths are spreading, and the only effective treatment is Kira's stem cells, and even that will only buy time for Ethan Duncan to develop a real cure. Rachel offers Delphine the position of interim program director, in Dr. Leekie's place, and Delphine is suspicious but accepts.
Delphine tries to convince Sarah and Mrs. S of the plan to use Kira's stem cells, Mrs. S is untrusting, but Sarah is fixated on the danger to Cosima. Delphine says any treatment from Ethan would be months away, and Cosima wouldn't last that long.
Cosima is on a video call with Sarah and Alison; she is getting oxygen, but says she's feeling better, though the others are concerned at how bad off she is. Donnie is with Alison, and prompts her to ask if there have been consequences of Dr. Leekie's death. Cosima says officially, he died on the Dyad private jet, there's no investigation to be done.
After the phone call, Donnie and Alison argue about what to do with Leekie's body. Donnie is trying to be clever for once, but Alison finds a flaw in each of his ideas. Alison's solution: bury him in the garage floor. They drill a hole in the middle of the garage, and start excavating dirt.
At the farm, Mark and Henrik talk, Mark has been having nightmares, and Henrik calms him down. Mark is glad that Henrik has given him a purpose, and Henrik is glad that Mark went AWOL from the military to join them. Henrik recognizes that Mark and Gracie are fond, and blesses them, but says it's time for Gracie "to bear fruit", and asks Mark if he is ready to be with her as a husband.
Sarah and Mrs. S discuss Kira, and Mrs. S knows someone at a pediatric clinic who could do it, so they wouldn't go near Dyad. They recognize it should be Kira's choice, and Sarah explains it to Kira, including the pain and risks. The clincher is that, without it, Cosima could die. Kira says OK.
The bone marrow removal is done at the pediatric clinic, Delphine there only to take the samples to Dyad. Kira will stay overnight, and Sarah and Felix stay with her, with Mrs. S and Benjamin guarding.
At Cosima's lab in Dyad, Scott puts together equipment to read Ethan's old floppy disks; he gets data, but it looks like random garbage. Ethan glances at it and says it's correct, it's encrypted, and he has the key in his head. Scott can make an algorithm to decrypt it.
As Alison and Donnie are digging, they hear that Vic has been asking for them. Donnie finds him peeking into the garage window, and threatens him with his gun. In the garage, Alison tells Vic he's harassing her family, and Donnie (perhaps being too macho) threatens to shoot him. Vic says the detective, Angela, has been squeezing him, he has to do something. Vic leads Donnie to Angela's van, and Donnie complains that she and Vic have been harassing Alison. Angela says this is business, but Donnie doesn't think so, Art Bell was suspended for investigating this, and Angela doesn't want to know what Donnie and Alison know. He says, come near my family again, and I'll bury you. He takes their picture and leaves, looking content with himself.
Henrik Johanssen uses insemination equipment to implant an embryo into Gracie, just as he did with Helena. When it's done, she looks stunned, and is given a new bed, in the same room as Helena. Helena is surprised that Gracie is sad to be pregnant, and Gracie explains: my father is the father, I'm carrying your babies. Helena isn't happy with this.
Scott finishes decrypting the sequence from the floppy, and Ethan says he can now begin correcting his mistakes. Rachel's guard asks about decrypting the other sequences, and Ethan says they each have different keys, and he's not ready to reveal them to Dyad yet.
Delphine returns to her office, which Rachel has been using, and tells Rachel the bone marrow is being processed. Rachel is interrupted by her phone, and Delphine notices what Rachel had on her desk monitor: a dossier on Mrs. S's friend Benjamin, marked "asset".
Donnie and Alison finish moving Leekie's body into the hole; they fill it with dirt, cover with cement, and make everything right again. They've done it. Alison is suddenly attracted to Donnie, and they grab each other and make love, there in the garage.
In Helena's room, she says she's leaving to her sestra, and Gracie says she's coming too. Henrik comes in, and says they should go back to bed. Gracie says she's not afraid, and Mother has gone west to find more "broodmares". Henrik knocks down Helena, grabs Gracie, and locks her in the cell.
Mark comes in, and Henrik tells him to keep away from Gracie. Mark objects to Henrik putting his own child into Gracie. As they talk, Helena comes up behind Henrik and attacks him. They struggle, Mark releases Gracie and they escape.
Henrik wakes up, bound to the table where he implanted embryos into Helena and Gracie. Helena plays with the instruments, and tortures Henrik with them for a while. Later, we see her on the hillside, looking back at the farm, engulfed in flames.
At the clinic, as Kira sleeps, Sarah gets a call from Delphine. She goes down to the street, where Delphine warns her that Benjamin is compromised.
As this happens, Rachel, disguised as Sarah, goes to Kira's room, knocks Felix unconscious, and takes Kira. The real Sarah arrives and finds Kira gone.
The next day, Cosima wakes up, and Delphine is crying; she says she's made a terrible mistake.
Kira wakes up in a pink bedroom, and Rachel is there, who says Kira will come in time to like it here, just like Rachel did.
- This is the last episode in which Vic appears, but Angela will appear once more.
- This is the last episode in which Henrik appears, he is surely dead. But Bonnie will be back.
- Tatiana Maslany as Sarah Manning/Cosima Niehaus/Alison Hendrix/Helena/Rachel Duncan
- Jordan Gavaris as Felix Dawkins
- Evelyne Brochu as Delphine Cormier
- Maria Doyle Kennedy as Siobhan Sadler
- Michael Mando as Vic Schmidt
- Michelle Forbes as Marion Bowles
- Peter Outerbridge as Henrik Johanssen
- Skyler Wexler as Kira
- Kristian Bruun as Donnie Hendrix
- Inga Vadranel as Angela Deangelis
- Josh Vokey as Scott
- Julian Richings as Benjamin
- Ari Miller as Mark
- Zoé de Grand Maison as Gracie Johanssen
- Kathryn Alexandre as Tatiana Maslany's Acting Double/Alexis
- Millie Davis as Gemma
- Drew Davis as Oscar
- Danny MacDonald as Martin
- Sadie Munroe as Faith
- Anita La Selva as Dr. Parks
- John Nelles as Dialogue Coach
- Cynthia Galant as Young Rachel
- The title is from Francis Bacon's Novum Organum.