Paul digs and finds the ugly truth behind the Castor Boys’ log books of names, pushing him into action. Meanwhile, Felix is desperate for info on Sarah’s whereabouts, and presses the still-ailing Rachel for any shred of a lead. In order for Donnie and Alison to take their money-making endeavor to the “next level” she must introduce Jason Kellerman to her unique business plan.
This episode contains examples of:
- Amicable Exes: Subverted. Cosima and Delphine aren't outright hostile to each other, but there's definitely tension between them.
- Anguished Declaration of Love: Paul gives one to Sarah.Paul: It was never Beth I loved.
- Anyone Can Die: While the threat of death has been present very in the show, the main characters have been fairly safe. The death of Paul (who was there since the first episode and had third billing in the opening credits) has since made it very clear that no one is safe.
- Babies Make Everything Better: Subverted. Though she was always taught that she was meant to have children, Gracie doesn't really want them.
- The Bus Came Back: Kira video-chats with Felix and Mrs. S, making it the first time we've seen her since 3.02. She's also part of Sarah's nightmare, but its not the real Kira.
- Call-Back: Sarah's dream about Beth ends with Beth walking toward the light the same way she walked toward the train.
- Card-Carrying Villain: Rudy gladly admits to knowing that his defect sterilized the women he slept with.
- Clingy Jealous Girl: Delphine has been stalking Cosima and her new girlfriend Shay.
- Conscience Makes You Go Back: After abandoning her in the last episode, Helena comes back to free Sarah.
- Continuity Nod: Felix confronts Rachel and references the time when Rachel disguised herself as Sarah and drugged him so she could kidnap Kira.Felix: You know, it's funny. Your hand was a lot steadier when you were jamming that needle into my neck, wasn't it?
- Death in the Limelight: This episode focuses heavily on Paul, and he dies at the end.
- Green-Eyed Monster: Donnie admits to being jealous of Jason Kellerman.
- Heroic Sacrifice: Paul unpins a grenade, destroying all the research on the Castor pathogen.
- Hollywood Healing: Averted. Mark is still healing from his gunshot wound, so he spends this episode walking on a cane.
- Jerkass Facade Has A Point: When Cosima snipes at Delphine for showing up five days after Sarah has disappeared, Delphine points out that nobody told her Sarah was missing.
- Kick the Dog/Took a Level in Jerkass: Felix's taunting of Rachel is surprisingly cruel. She actually starts to cry.
- Killed Off for Real: Paul, Miller, and even Pupok.
- Mushroom Samba: Sarah hallucinates about chasing Kira around the empty Castor base, which turns into a nightmare about Rudy giving a blood donation to her. Then, she has a vision of Charlotte leading her to Beth, who discusses her life and death.
- My Greatest Failure:
- Despite not being in love with Beth, Paul regrets her death.
- Sarah details how much she regrets leaving Kira for almost a year.
- Neck Snap: How Paul kills Miller.
- Oh, Crap!: Rudy and Coady high-tail it when Paul reveals he has a grenade.
- Precision F-Strike: Felix's reaction when Rachel struggles with her aphasia to say his name.Rachel: Ffff...Ffff...
Felix: Yeah, "Ffff" you, too. - Rasputinian Death: Paul gets stabbed in the guts, shot four times in the chest, and blown up with a grenade.
- Deader than Dead: With most of the show's deaths being characters that were evil or minor, along with Kira, Helena, and Mark all having seemingly fatal encounters that they survived, this could have been the writers making it clear that no, Paul will not come back in the next episode.
- Redemption Equals Death: When Paul finds out Castor is sterilizing innocent women in the hopes of creating a biological weapon, he frees Sarah and destroys Coady's research, at the cost of his life.
- The Reveal:
- The Castor clones sexually transmit a pathogen that sterilizes women they have sex with. Virginia Coady is trying to find a use for it as a bio-weapon.
- Rachel, slowly recovering from her brain injury, has been painting certain symbols that somehow correspond to Ethan Duncan's cipher for unraveling his synthetic sequences in his copy of The Island of Doctor Moreau, although she doesn't seem to have realized this yet.
- Rule of Symbolism: The long narrow escape tunnel with the light at the end is reminiscent of a birth-canal, with the symbolism becoming more apparent when the twin sisters are reunited within it.
- She's Back: After spending all season suffering at the compound and being goaded by Pupok, Helena devours the scorpion and goes back to save Sarah as her Leitmotif plays.
- Well-Intentioned Extremist: Coady hopes to isolate the Castor pathogen as a biological weapon that'll end wars.
- Wham Episode: Paul dies destroying Coady's research on the Castor pathogen, which makes women infertile.
- What the Hell, Hero?: Paul is horrified when he learns that Coady's been using the Castor clone's defect to sterilize innocent civilian women, with the intent of converting it into a biological weapon.
- You Have Outlived Your Usefulness: Helena, lost and exhausted in the desert, finally wearies of Pupok taunting her about leaving Sarah behind — and eats him.
- Which also turns Helena's "sandwich" story in the previous episode into a Brick Joke.
