Sarah's last chance to bring her nemesis back to sanity slips away as Art intervenes to get answers of his own. Meanwhile, the Orphans must decide whether to make peace with their creators, as Sarah is forced into a deadly confrontation with their enemy.
Sarah takes Amelia down to the basement of Mrs. S's house where Helena is being held. They argue, trying to convince Helena that Amelia is their birth mother. Mrs. S snoops through Amelia's luggage while they are in the basement and pulls out an envelope from a book. A picture in the envelope reveals an aged picture of 2 scientists until Kira comes downstairs and surprises Mrs. S.
Suddenly, a banging on the door interrupts Sarah and Helena. Art and the police burst in with guns and arrest Sarah. In the meantime, Helena has managed to pull herself free of her restraints and escape out the window of basement.
Art interrogates Sarah at the police station. He shows her a picture of the German Katya, demanding to know who she is. Art claims Sarah is the prime suspect for the murder. He forces her to tell him everything by threatening to make Kira motherless and charging Felix for abetting.
Alison is working out to a video until the doorbell rings. Dr. Leekie is at the door and asks to come in. He offers Alison a contract (Dr. Leekie calls it a "treaty"). Since Alison wants her old suburban life back, she listens. Dr. Leekie offers her protection from Helena and other threats, as well as removing her monitor. In return, she will be subject to noninvasive testing twice a year. As a gesture of good faith, Dr. Leekie says her monitor has already been removed.
Felix is interrogated at the police station by Angela about his false identification of Beth's dead body as Sarah. He lies, claiming a case of mistaken identity. They banter and Felix insults Angela, telling her she needs to get laid. Angela intends to arrest him and calls a public defender for him.
Cosima is leaving the bus station. She begins to cough up blood like Katya. She is ambushed by Dr. Leekie, who offers her a ride while they discuss an agreement. Dr. Leekie offers her a job at the Dyad Institute and her complete sequenced genome, offering her freedom to research the clones.
At the police station, Art plays back Sarah's recording to her. She had earlier recorded a message on her phone, telling Art that he was the only one she trusted, and the only one who could figure everything out. As Sarah is about to reveal everything to him, the interview is interrupted by Daniel Rosen, a lawyer who works for Dr. Leekie. He has Sarah immediately released before she says anything to Art.
The lawyer takes Sarah to a building where they meet with Paul. Paul tries to convince her to listen to their offer, saying he has to work with Dr. Leekie since they can still blackmail him for his time in Afghanistan. They leave Sarah on a dark office floor with a woman standing in the corner. The other woman is revealed to be another clone, Rachel Duncan. Rachel offers Sarah "mutual disclosure" and "topside". Rachel says that they want to transition Sarah to "self-awareness". They will answer any questions for Sarah and give protection from Helena and the Proletheans, and Sarah will willingly work with them. Rachel implies that Kira could be harmed, and Sarah rejects the offer. Rachel gives Sarah 24 hours to think about it.
Alison, Sarah, and Cosima meet up to discuss the contracts at Felix's loft. Alison tells them she is likely to take her contract to keep her children safe. Cosima says her offer to study clone biology is tempting, but seems unsure. Cosima warns Sarah that Rachel's offer may be a red herring. Their true interest may be in Kira because she is the first documented child of a clone. Cosima receives a notification on her phone that Delphine has skipped her flight.
Art and Angela identify the German as Katya, but are unable to pursue the lead since it falls under federal jurisdiction. They decide to focus on Sarah Manning, since Art has found her association with Vic. They find Vic at a Narcotics Anonymous meeting as he shares his story. When Art and Angela threaten Vic with his outstanding warrants, he says the last time he saw Sarah was in Scarborough, posing as a suburban wife.
Alison sees Ainsley's house has been sold when she takes out her recycling. Ainsley is packing in her garage, and Alison walks over to talk. Chad and Ainsley have separated. Alison confronts Ainsley, accusing Ainsley of being her monitor. They get into a fight, and Ainsley begins to throw away a Christmas angel Alison had made for her as a gift into the sink garbage disposal. As Ainsley attempts to fit it down the drain, her scarf gets caught and begins to choke. She begs Alison for help, but Alison stands by to watch.
Art and Angela stake out Alison's house. As Alison comes out to get her mail, they realize that Alison is not Sarah Manning.
At Mrs. S's house, Sarah packs up a bag for Kira. Sarah tells Kira that they have to hide the bag in case they have to run away and not to tell anyone, even Mrs. S. As Sarah leaves to meet Amelia, Mrs. S gives Sarah a warning to watch herself with Amelia.
At Felix's place, Cosima is coughing up blood in the bathroom when Felix walks in. She assuages him, saying she's fine. Delphine comes to meet Cosima at Felix's. Delphine says that she won't work with Dr. Leekie anymore and is on Cosima's side. Delphine says the genome sequence that Dr. Leekie gave Cosima does not exist anymore because he deleted it. Cosima says she doesn't think it's a sequence, but a message. Cosima thaws and allows Delphine to help.
Sarah meets Amelia at Beth's house. Amelia warns Sarah about Mrs. S, she is not who she seems to be. As Amelia is about to show Sarah something, Sarah begins talking with a Ukranian accent, asking how scientists put babies in her and stabs her. Amelia pulls off her wig, and reveals Helena. Helena blames Amelia for giving her away to the Proletheans and making her this way. Later at night, Sarah walks into Beth's apartment and finds the floor covered in blood. Helena calls and tells Sarah to meet her and Amelia.
Alison is still shocked from Ainsley's death when Donnie walks in. They reconcile and decide to make a fresh start.
Cosima is decoding the sequence, but cannot decipher the barcode as nucleotides. However, Delphine says she knows Cosima's personal identification code 324B21. Using this information, Cosima attempts to run a decryption program, but nothing works. They make a breakthrough when they realize the data encoded must have been done 30 years ago. Therefore, it likely would not have been done in nucleotide sequence, but in binary in ascii.
Sarah goes to meet Helena in a warehouse. She finds Amelia slumped against a pillar. Before she dies, Amelia hands Sarah a picture of Mrs. S as a scientist from 1977 (the same picture Mrs. S saw when she looked through Amelia's luggage). On the back of the picture, the names are blacked out, but their titles as professor are typed out, as well as Project LEDA. Helena comes down the stairs with a torch. After Sarah insults Helena, Helena slams Sarah to the floor and chokes her with a chain. Because they are sisters and family, Helena says she cannot kill her, just as Sarah could not shoot Helena when she was in the cage. As Helena walks away, Sarah shoots her, saying she already has a family. Helena dies.
Sarah calls Rachel, saying she doesn't want Kira to live like this. Rachel agrees, telling Sarah to come in.
Alison signs her contract as ambulance and police come to recover Ainsley's body. Rachel receives a scan of Alison's contract.
At the building to meet Rachel, Paul escorts Sarah from the elevator. He tells Sarah about Afghanistan. He was a private contractor who killed 6 marines through friendly fire.
Cosima finally deciphers the sequence and discovers that Dr. Leekie and his colleagues have patented the clones. She calls Sarah and tells her she cannot make any deal with them. As the elevator door opens to Rachel's floor, Sarah and Paul have disappeared. Rachel receives an email from Sarah "Up yours proclone". Rachel makes a call, saying "You know what to do".
Sarah walks into Mrs. S's house, but it has been ransacked and everyone is gone, including Kira.
- Tatiana Maslany as Sarah Manning/Alison Hendrix/Cosima Niehaus/Helena/Rachel Duncan
- Dylan Bruce as Paul Dierden
- Jordan Gavaris as Felix Dawkins
- Kevin Hanchard as Arthur Bell
- Michael Mando as Vic Schmidt
- Maria Doyle Kennedy as Siobhan Sadler
- Matt Frewer as Dr. Leekie
- Skyler Wexler as Kira
- Kristian Bruun as Donnie Hendrix
- Natalie Lisinska as Aynsley Norris
- Inga Cadranel as Angela Deangelis
- Ron Lea as Lieutenant Hardcastle
- Evelyne Brochu as Delphine
- Melanie Nicholls-King as Amelia
- Josh Vokey as Scott
- Matthew Bennett as David Rosen
- John Nelles as Dialogue Coach
All songs for the episodes have been verified by TuneFind(A reliable Slsource)
- "La petite mort" by Cœur de pirate
- "Blame Fiction" by The Belle Game
- "Orphan Black Finale Theme" by Trevor Yuile
- "Previously On" by Trevor Yuile
- "Kira's Cue" by Trevor Yuile
- "Helena's Melody" by Trevor Yuile
- Based on the date on the contract seen on this episode, this season was set in 2012, with this episode particularly on December 16, 2012.