A flashback to Beth Childs' final investigation, days before her suicide.

After fleeing Iceland, Sarah begins searching for M.K. and uncovers new clues to Beth's breakdown. Scott learns Kendall Malone is hiding something.

As Sarah scrambles to learn more about her implant, Alison and Donnie take a drastic step to help. Meanwhile, Kira has a disturbing vision.

While Cosima examines Leekie's body, Felix and Donnie pose as a couple to learn more about a fertility clinic. Sarah discovers M.K. has her own agenda.

A risky cover mission at Brightborn yields several big surprises. The rift between Sarah and Felix grows as she checks up on Adele.

Seeing that it is the best overall solution yet not perfect by any means, Sarah and Cosima decide with Kendall's OK to set up an agreement with Susan Duncan, which they will not divulge to Mrs. S. until everything is arranged as they know she won't like what they've done. That agreement is an agent representing Susan will remove the bot from Sarah's cheek, with Cosima on site to ensure Sarah's safety. As Scott and Cosima have not yet come up with a "cure" for Cosima and the other affected Leda clones, they in turn will provide their research and Kendall to Susan, with Scott harvesting the necessary cell from Kendall so that Susan can continue the work on curing the affected Leda clones. The agreement does not include providing any of Kendall's DNA for the Castor project. When these two sides of the agreement are accomplished on neutral sites, Susan's agents will release Cosima, while Kendall will be whisked away to safety back at the safe house. While those involved hope to get what they want out of the agreement, they may be unaware that there is at least one other person in the know who may have a different view of the Leda project and Kendall's utility. Meanwhile, Krystal is in the police precinct to report what she believes is going on with the illegal use of stem cells in cosmetics production. Art is able to intervene so that Krystal feels like her issues are addressed, while anyone who may have known Beth will not be suspicious. Art feels he needs to call in support, the person to the rescue being the one who may most be able to placate Krystal.

Sarah regresses to old habits while struggling to cope with the consequences of her decisions - reconnecting with Beth on a dark night of the soul. Back at the lab, Cosima, haunted by vicious memories and news of Delphine, attempts a dangerous Hail Mary to find a cure. At the Hendrixes, Alison is more determined than ever to create normalcy for her kids. As she forges ahead with a birthday party, Donnie is caught in the Neolution crosshairs.

Siobhan wants vengeance for her mother. Cosima and Susan Duncan try to come together to try to finally find the cure. Neolution continues with their threats causing Alison to be terrified, and Mrs. To question her loyalty to her sestras.

The formal alliance between the sisters on one side Susan/Rachel/Ira on the other side begins in earnest. Cosima has arrived on the island where she and Susan will begin the process of finding a cure for both Leda and Castor by developing original DNA in the absence of Kendall through fertilization of one of Sarah's eggs with Ira's sperm, while Sarah and Felix meet with Rachel and Ira to discuss the next step in bringing down Evie Cho and restoring Susan as the head of Neolution. As Evie ramps up her media campaign to bring BrightBorn's work to the masses, Sarah, Rachel, Felix and Ira learn that two women, Tabitha Stewart and Kendra Dupree, have escaped from BrightBorn's facility, Tabitha near the end of her pregnancy and Kendra with her newborn. Rachel believes that what Tabitha and Kendra know and bringing it to public light is the key to exposing Evie's work. Sarah is determined for "her side" to do the work in finding the two women despite Sarah being Evie's primary target, having her side being down in human resources with both Cosima and Alison out of commission and Helena still MIA, and knowing that Evie has her operatives also tracking the two escaped women. Through the process, Sarah and Rachel still display obvious animosity toward each other. They will learn if their mistrust of the other is warranted. Meanwhile, Donnie has been released from remand with Adele still tasked with leading their legal team. In her reunion with her husband, Alison comes to some realizations about her current life, and with Donnie has to make some decisions about how to rectify what has been missing of late. Felix comes to a decision of his own about his personal life as he and Adele help the Hendrixes and as someone unexpectedly shows up on his doorstep. And Rachel continues to see visions, still of the swan but the visions more fully realized, but still without fully understanding why she is having these visions and what they mean.

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.