Mark is taken down in a Prolethean shoot-out and Sarah must step in to help. But as Sarah gathers intel that puts her on the trail of the original Castor DNA, a familiar foe is not far behind. While Helena continues to toil in a faraway military compound, it is ultimately Sarah’s fate that will hang in the balance as she tries to save her sister. Meanwhile, Gracie is cast out from the Prolethean fold, and Alison and Donnie come face-to-face with unhappy drug lord, Jason Kellerman.
This episode contains examples of:
- The Atoner: Part of the reason Sarah's so determined to save Helena is out of regret for shooting her and for assuming that she was a monster.
- Body Horror: Parsons' entire scalp was removed and he had wires going into his brains.
- Chekhov's Gun: The steak Helena was eating at the start of her episode. She chews down the bone into the shape of a key to escape her cell.
- Cliffhanger: At the end of the episode, Sarah is left at Rudy and Mark's mercy.
- Convenient Miscarriage: Gracie loses her baby. Which it later turns out is more related to the ongoing CASTOR plot of the season than just a convenient miscarriage.
- Determinator: Helena fights off the force of her sedatives through tourniqueting and sheer will, as personified by Pupok, but unfortunately the drugs win out.
- Death of a Child: Henrik and Bonnie's first son died in the crib. When his grave is dug up, tiny bones are found in a coffin small enough to be carried by hand.
- Enemy Mine: Sarah and Mark end up working together for the episode. By the end however, he betrays her to Rudy.
- A Fate Worse Than Death: Helena finds a Castor clone named Parsons strapped to a chair with his brain exposed and plugged with electric wires. He begs her to kill him and she does. Then she calls out Coady for keeping him alive against his will.
- Genre Savvy: Helena ties off the blood flow to her arm to slow the release of Coady's sedative as part of her escape plan. She later gets out of her cell with a steak bone chewed down into the shape of a key and manages to avoid the security cameras while doing it.
- Heroic Sacrifice: Helena throwing away her chance at escape to grant Parsons the gift of peace.
- I Need a Freaking Drink: Sarah gulps down some alcohol before doing surgery on Mark, the same alcohol they later used to clean his wound.
- Meatgrinder Surgery: Sarah must remove a bullet from Mark's leg with nothing but a pair of pliers for forceps, and a bottle of booze to sterilize the wound.
- Mercy Kill: Helena kills Parsons, the Castor clone she found, at the risk of her own escape, because he begs her to.
- Not Quite Dead: After it's implied that Bonnie finished him off, Sarah finds Mark alive but wounded in the cornfield.
- Oh, Crap!:
- Sarah's reaction when Bonnie sends some more Proletheans into the cornfield to go after Mark.
- Again when she turns around to find Rudy pointing a gun at her.
- Gracie when she starts bleeding between her legs and realizes that she's having a miscarriage. Also Bonnie's reaction when Gracie falls over in pain.
- Old Flame: The drug lord that Alison and Donnie are forced to face turns out to be Jason Kellerman, Alison ex-boyfriend from high school.
- Posthumous Character: Abel Johanssen, Henrik and Bonnie's son, whose genetic material came from the Castor original.
- Precision F-Strike: Helena to Coady, for keeping the captive Castor clone alive against his will.Helena: You're a shit mother.
- Prophet Eyes: Jonah Appleyard, the old blind man that the Proletheans from the Johanssen ranch are staying with after the fire.
- Relativ Button: Invoked twice. Kellerman's henchman and Rudy talk about Alison and Sarah's kids in order to intimidate them.
- Retcon: Alison tells Jason that she met Donnie in college, contradicting what she told Sarah in season one about meeting him in high school.
- The Reveal: Henrik Johanssen was Ethan Duncan's assistant during the Leda experiments and used the biological samples to try to make more Castor clones. One son was born, but died as an infant.
- Rule of Symbolism: Gracie taking off her wedding ring.
- Self-Surgery/We Have to Get the Bullet Out!: Sarah is forced to help Mark get Bonnie's bullet out of his leg.
- Shout-Out: Breaking Bad is referenced during Alison and Donny's discussion of their business.
- Sibling Rivalry: There's implied to be one between Mark and Rudy, though it turns out to be a Secret Test of Character.
- Squick: In-universe. Let's just say becoming a trauma surgeon is not on Sarah's to-do list.
- Tantrum Throwing: Part of Helena's plan. She throws a tantrum in her cell hoping to get put in the infirmary for Self-Harm. With her arm tied off, the drugs don't get into her bloodstream as quickly, and she's able to start escaping.
- You Have Outlived Your Usefulness: A non-fatal version. Once Gracie miscarries, the Proletheans exile her. They only wanted her for the baby.
