Season 5

1. The Few Who Dare

Sarah finds Cosima in Revival, a civilized village on the Island. She is told Revival chooses their residents for the betterment of science. Cosima decides to stay there to access the advanced medical science at Westmorland's disposal after having seen Delphine's bullet wound has healed almost completely. Rachel becomes the spokesperson for P.T. Westmorland. Felix and Ira try to contact M.K. Siobhan fends off Ferdinand with a corkscrew. Art gets a new partner, Detective Engers, who is actually working for Dyad. Engers captures Alison in an attempt to apprehend Helena. Donnie and Helena elude Engers but Helena is stabbed in the stomach. Sarah tries to escape the island but is captured by one of Rachel's men with a dart.

2. Clutch of Greed

With Sarah and her family taken captive by Neolution, Rachel offers to let them live in peace as long as Kira submits to occasional testing. Refusing to allow this, Sarah, Felix and Siobhan conspire with M.K. to retrieve Kira from school before Rachel and Ferdinand can. Their plan is successful, but M.K. stays behind at Felix's loft to distract Ferdinand, who brutally kills her, for which Rachel ends their relationship and fires him. Sensing M.K.'s death, Kira forces Sarah to take her back to Rachel for testing so she can understand herself. Meanwhile Donnie takes Helena to the hospital, where her unborn babies heal rapidly. Suspicious that the doctor treating her may be a Neolutionist, Helena attacks her and flees. On the island, Cosima meets P.T. Westmorland. Delphine meets with Siobhan in secret.

3. Beneath Her Heart

Struggling with her feelings of uselessness to her sisters, Alison is sidelined in her neighbourhood's carnival celebrations, and her guilt over Aynsley's death resurfaces when Chad shows up at the carnival, leading her to relapse and get high with help from Ramone. Meanwhile Art is forced to assist his partner in searching Alison's house and planting evidence tying her to Pouchie's murder; instead his partner discovers the corpses of Leekie and Rudy under the garage. Donnie collapses while performing a highland dance onstage, after accidentally consuming a drink Alison spiked with tranquilizers.

Alison berates the watching crowd for their hypocrisy in criticising her and her husband, reminding them that most of them bought drugs from her. She then confronts Rachel and demands she call off the police, pointing out that an investigation into Leekie's murder will draw unwanted attention to Neolution and get Rachel into trouble with Westmorland. Alison later decides to leave for a while, with Donnie's blessing.

4. Let the Children and Childbearers Toil

Frustrated Kira won't tell her what she does with Rachel, an irritated Sarah is taken by Siobhan to con their way into a mental hospital to see a patient who has information on Westmorland. Visiting Helena in a convent along the way, Helena tells Sarah that Kira's connection to the Ledas is special and Kira will have to eventually deal with what the clones do. The patient is Dr. Virginia Coady, drugged and hidden there by Susan Duncan to keep her away from Westmorland. Before the cloning work began, Coady and Westmorland pushed a boy with a perfect genome too far despite Susan's protests.

Adele returns having learned about the clones from Siobhan and recruits Felix to go to Switzerland with her to track Neolution companies. Susan awakes on the island, Westmorland needs her scientific mind for Kira's data but Rachel is still in charge of the project. Cosima follows Mud around, eventually seeing the perfect boy is now a feral adult living in the woods.

5. Ease for Idle Millionaires

Delphine returns to the island but refuses to tell Cosima about the endgame plan and they accept the flaws in their relationship. Westmorland injects Rachel with the cure. Cosima realizes the man in the woods, Yanis, has a healing factor. At a dinner party held by Westmorland, Susan admits to trying to give it to the clones but it ended up passing to Kira. Westmorland's plan is to have Kira's eggs harvested to 1300 surrogates to control the healing factor. Ira begins glitching. Cosima is able to glean Westmorland's immortality is a lie and that's why he really wants to use Kira.

Westmorland kills Yanis and locks Cosima in his cage. Meanwhile, Sarah offers to be more honest with Kira if she explains more about her link to the Leda clones; Kira wants to be a hustler like her mother. Delphine heads for Switzerland, but warns Siobhan that Kira is running out of time.

6. Manacled Slim Wrists

Krystal and her roommate Brie stumble into a current Dyad scheme involving cosmetics and the plan for Kira. Sarah and Art are forced to watch as Krystal takes charge in the hunt for answers. It turns out Neolution wants to spread Kira's genes to people through dermatology products. Rachel is temporarily fooled into letting Kira stay home but takes her from Siobhan after a call from Westmorland. Siobhan warns Rachel that she will need help one day. Meanwhile on the island, Dr. Coady returns much to Susan's chagrin and once Susan learns Westmorland is taking children's blood to extend his own life she prepares to kill him.

Cosima and Ira persuade Mud to help them kill Westmorland, but she backs out. Cosima and Charlotte sail away after Cosima shows the Revival villagers Westmorland's immortality is a lie, and they riot. Ira finds Susan dead in the mansion as his glitching goes critical, Ira's fate is unclear.

7. Gag or Throttle

Rachel returns to the island, meeting Coady after visiting Susan and Ira's graves. Though Westmorland promised her freedom and called her a daughter she still feels like part of the experiment. Flashbacks reveal she always struggled against it and could never get acceptance as an equal. Mark is brought to the island after making a deal with Coady for a Castor cure, Gracie visits Helena. Westmorland demands Kira be brought to him, and Rachel is horrified to learn her new eye has a camera to let him see and hear everything she does.

Alison returns with a new look and attitude, shocking Donnie; while Cosima and Charlotte show up to continue research into Westmorland's origins. Sarah gets wind of what is planned for Kira and Cosima sends her Westmorland's real identity. Sarah emails this to Rachel at Dyad, but knowing Westmorland is spying, Rachel acts unmoved. Rachel drugs Kira but sends Art a message with her head turned away. Rachel wears an eye patch to release Kira to her family. Rachel exposes Westmorland to the rest of his backers and bloodily cuts out her prosthetic eye.

8. Guillotines Decide

Ferdinand rescues Rachel from Dyad. Though Sarah is suspicious, Siobhan wants everyone to focus on the opening of Felix's art show that night. Siobhan and Delphine are revealed to be working with Ferdinand as a source. Their efforts have finally figured out Neolution's ultimate goals but they need hard data from Rachel to prove it all and warn the world. Ferdinand says he and Rachel can use this to blackmail Westmorland's backers and build an empire. Rachel betrays him and gives the real data to Siobhan to bring down Neolution.

Delphine and Cosima then upload it. Sarah, Alison and Cosima become performance art posing as one person in Felix's show. Felix thanks his family for their support, especially Siobhan for taking him and Sarah in as children. Meanwhile, Gracie decides not to betray Helena but the Neolutionists trace her phone, capturing Helena, and Detective Engers kills Gracie. Ferdinand attacks Siobhan in her home and the two kill each other. Sarah senses Siobhan's death.

9. One Fettered Slave

After Siobhan's funeral, the sisters learn Helena has been kidnapped and that Neolution is trying to force the immediate birth of her twins. Westmorland's backers have started to be murdered but Felix and Art are able to get information with Rachel's help. They are hiding Helena in the abandoned asylum wing next to Dyad's main building, which is swarming with police and media with Neolution exposed. Sarah, disguised as Rachel, is taken there by Detective Engers. However, Sarah is caught before she can kill Westmorland/Mathieson. Meanwhile, Coady follows orders and euthanizes Mark, ending the Castors. Helena slits her wrist to die so her babies won't be abused like she was, but she is saved with Sarah's blood. Scott and Hell-Wizard sneak into Dyad to let Art inside the old wing. Helena bashes Coady's head against the gurney, and before she and Sarah can escape, her water breaks.

10. To Right the Wrongs of Many

Art sneaks in, knocks out Engers and finds Helena. Coady finds them and forces Art to tend to Helena at gunpoint, but the two work together and Art disarms Coady while Helena finally kills her by jamming a screwdriver into her neck. Sarah battles and kills Westmorland/Mathieson by crushing his skull with his own oxygen tank, saying the sisters survived and evolved beyond him. Sarah and Art help Helena deliver two healthy twin boys. Months later, Helena is living with the babies in the Hendrix garage and the clones and their allies meet for Helena's baby shower.

With no conflict left to focus on, Sarah feels like the same failure of a mother and wants to run again. Her sisters calm her, so she happily stays. Rachel meets with Felix to give him the list of all 274 Ledas in the world. Though not part of the group and without her elitism anymore, Rachel is free. The sisters' journey ends as Alison and Donnie enjoy their happy marriage; Charlotte is taken in by Art; Helena names her babies after Arthur and Donnie; Cosima and Delphine travel the world curing all the unaware Ledas; and Sarah and Felix take Kira for a day at the beach.