When Rachel makes a promise to Sarah, it comes with a hefty price. Meanwhile, Helena and Gracie work with the Hendrixes, and Donnie takes Kellerman to task. Over at Castor, Coady and Benchman scheme to track down the Castor Original, and Rudy descends on DYAD for a much needed asset.
Delphine is getting a manicure from Krystal Goderitch, the Leda clone attacked by Seth and Rudy. Delphine is assessing Krystal, a typical bubbly valley girl, who describes to Delphine her encounter with the Castor clones. Krystal tells her how she was about to be abducted by Seth and Rudy, who thinks were identical twins, but hotel security, actually DYAD officials, stopped them. However, her monitor was killed in the process.
Virginia stops by the same bar Sarah and Helena were at, looking for them. She is meeting with David, the guy in charge of Castor. Virginia informs him that without the original genome, which was incinerated by Paul, the Castor clones will all be dead in a year and a half, two if they’re lucky. David asks her about Rudy, who Virginia mentions is in the field. David then tells her that he has a source inside Leda, which completely surprises Virginia. Virginia muses about how she doesn’t think Castor and Leda are just two factions and asks David who is actually in charge of all this. But David just tells her to keep the Castor clones alive.
After her manicure, Delphine meets with Dr. Nealon, and informs him that Krystal remains clueless about what happened to her and has explained away her encounter with Seth and Rudy. Nealon tells Delphine that Rachel is getting better, but Delphine sees that as a threat.
Cosima and Sarah are video-chatting. Sarah is worried about Cosima’s health, but Cosima dismisses her concerns, saying that her recent health issues were totally normal and it’s a trend, so she should be fine. Cosima assures her that Delphine and others are working on a cure. Sarah is still bothered, and says she can’t lose another one of them, and Cosima reassures her that they won’t lose anyone. Seeing Shay enter, Cosima tells Sarah to call Scott and gets off.
At Alison’s house, although Alison is willing, Donnie does not want Helena in the house. Felix tries to convince him, saying that it’s their turn to take care of her. When Donnie still doesn’t agree, Felix tells him that if they don’t take Helena in, he’ll tell everyone about their pill business and so Donnie gives in. Meanwhile upstairs, Gemma is picking out clothes for Helena and we see that Helena still has her eggs that were extracted from her, in a nitrogen case and carts it around everywhere. Dressed in Alison’s clothes, Helena descends down the stairs. Cosima asks Shay if she knows about near death experiences. Shay says that she has this theory that when you have a near death experience, you see the one thing you truly love, love your soul can’t live without it, and if it’s strong enough then it pulls you back. This strikes a chord with Cosima since the last thing she saw was Delphine, but Cosima shrugs it off.
After getting off the phone with Cosima, Sarah calls Scott. Scott tells her about Duncan’s book and how Rachel is the only one who can translate it, but Rachel will only do it after talking to Sarah. Scott tells her that they haven’t told Delphine about the book yet because Cosima doesn’t trust her, but Scott thinks that they should. Sarah disagrees, pointing out that if they tell Delphine, she may tell Topside who can then restart human cloning once they decipher the book.
In Rachel’s room, Delphine notes that Rachel is getting better, making her more of a threat. After Delphine leaves, Sarah, along with Felix and Mrs.S video-call Scott who is also in Rachel’s room. Rachel demands that she will decipher the book and in return she wants a quiet life in Taiwan. But since Rachel has been pronounced dead, she can’t use her own ID and so wants them to steal Krystal’s ID for her. Sarah hesitantly agrees, but wants Rachel to show that she can indeed translate the book. Rachel proves to them that she can indeed decipher the book and decodes the page Scott gave her. It says, “In London town we all fell down, and Castor woke from slumber.” Mrs. S. doesn’t want to trust Rachel and also states that if they get Rachel out, it’ll destroy their alliance with Delphine, the only thing protecting them from Topside. But Sarah thinks that they have to, to cure Cosima and wants Felix to help her get Krystal’s identity.
Cosima takes Shay to her lab at DYAD where she introduces her to Scott. While showing her around, Shay finds Duncan’s book and picks it up. A panicked Cosima snatches it away from her and puts it in Scott’s bag before Shay can get a real glimpse. Delphine walks into the lab and asks Shay and Scott to leave because she has some really bad news for Cosima.
At Bubbles, Helena stashes the cylinder with her eggs behind one of the storage shelves before helping Donnie with making soap. As Helena helps Donnie, the two joke and it seems like Donnie is coming around to having Helena with them. Donnie then leaves Helena to confront Alison about Jason kissing her, and Alison tells him that although it’s fine, she’ll talk to Jason. But it’s clear that Donnie doesn’t trust Alison. Meanwhile, Gracie arrives for her first of work at Bubbles. She meets with Helena and apologizes to her for losing her baby. Helena forgives her, and asks Gracie to be her unborn baby’s aunt, to which she agrees.
Sarah takes Felix to the salon that Crystal works at to steal her wallet. Felix goes in looking for a manicure and pedicure from Krystal, putting on an American accent. Meanwhile, Scott arrives home to find Rudy at his apartment. Rudy demands that Scott give him the book, threatening Scott’s cat. Terrified, Scott breaks down and gives Rudy the book.
Back at the salon, Felix flirts with Krystal and gets her to share her first pet’s name and mom’s maiden name. Krystal also starts telling him all about her encounter with the Castor clones. Krystal admits that she feels like she’s missing something big. She tells Felix that although she may not be too smart, she’s not an idiot either and knows something is going on. Sympathizing with her, Felix wants to tell her everything but Sarah warns him not to drag her into the whole mess. Making up an excuse, Felix heads to the back room to steal Krystal’s wallet. Along with her wallet, he also finds a small notebook with notes she has taken about her run-in Seth and Rudy and realizes that Krystal has been investigating what happened with her. Putting up a lame excuse, Felix is about to leave, when Krystal starts crying, sure that her oversharing is driving him away. Felix lets go of his American accent and tells Krystal that she’s one of a kind and a survivor and runs off.
At DYAD, Delphine informs Cosima that the European team has been unable to device a gene therapy for the disease, and another clone from Poland has also succumbed to the disease. Delphine wants Cosima to take stem cell treatment from Kira but Cosima declines, stating that she will not harvest Kira anymore. Scott calls Delphine and tells her everything about the book.
Alison meets with Jason and tries to tell him that if he thinks there is something between them, he’s wrong. But Jason kisses her instead and though Alison kisses him back, she pulls away and reiterates that she is married. This angers Jason, who walks away.
Delphine and Cosima show up at Scott’s place. Delphine is infuriated at Scott and Cosima for keeping the book a secret for so long. She asks them if they made a copy of the book, but Cosima tells her that they didn’t since they thought it wouldn’t be safe to. Scott also tells Delphine that Rachel is the only one who can read the book.
One of Scott’s gaming friends shows up at Mrs.S’s and hands them a packet, which turns out to be a copy of Duncan’s book. Sarah, Mrs. S. and Felix join in with Cosima on the phone and Cosima tells them that she’ll distract Delphine while Rachel is sneaked out of DYAD and brought to Mrs.S’s house.
An angry Delphine is meeting with Rachel and Scott in Rachel’s room. After Delphine finds out that Scott and Cosima showed Rachel a page of the book mentioning Castor, she is convinced that Rachel was the one to sell them out to Castor, since she has nothing to lose. Delphine gets called by Cosima and departs, leaving Scott and Rachel alone. With help from a friend disguised as a security guard, Rachel and Scott escape while Cosima distracts Delphine by offering up her resignation.
Donnie steals Alison’s phone and texts Jason to meet her in the storage room. Jason shows up, thinking Alison wants to meet him, but finds Donnie there instead. They get into a fight and Jason ends up knocking Donnie out. Jason panics and leaves him lying on the floor.
Delphine tries to convince Cosima to stay, pointing out that outside of the DYAD, she’s just another subject, and anyone can be a spy, talking particularly about Shay. Cosima replies that if Delphine’s not going to be with her then she should let her go. Meanwhile, Scott brings Rachel to Mrs.S’s place. Rachel starts translating more of the book. At DYAD, Cosima tells Delphine about her near death experience. Cosima tells her that she could’ve just slipped away that day, but she came back for Delphine. This resonates with Delphine and she kisses Cosima. Rachel translates a little bit of the book: “In London town we all fell down, and Castor woke from slumber. Find the first, the beast, the cursed, the original has a number. H46239”. Just then, Dr. Nealon shows up with a tactical team to take Rachel away. Nealon snatches the book from Rachel, telling them that Delphine knew they must’ve made a copy of the book. Suddenly, Rachel falls out of the chair and has a seizure. Nealon takes Rachel back to the DYAD and gives Delphine the copy, but Delphine is angry because Nealon assured her that Rachel could handle the move. Nealon then takes Rachel into surgery, and as the elevator closes, Rachel opens her eyes and Nealon and Rachel share a look. Later, Nealon informs Delphine that the stress was too much for Rachel and she suffered an intra-cranial bleed. So, they had to induce her into a coma to control the swelling, but she may never recover.
Delphine then meets with Cosima and Scott. Cosima tries to explain to Delphine that they didn’t give her the book because they didn’t want Topside to get a hold of it, but Delphine thinks that it would’ve been safer with her. The copy is secure but is useless since Rachel can’t read it. Delphine accepts Cosima’s resignation and fires Scott. Before Cosima leaves, Delphine gives her a file on Shay.
At Mrs. S.’ house, Felix, Sarah and Mrs.S realize that they need to go to London to solve the code. Meanwhile, Nealon gets on the phone with Rachel. It’s revealed that Nealon switched out Rachel for Krystal. So it’s actually Krystal that is in the induced coma, and Rachel is getting surgery for a prosthetic eye.