Sam and Dean help Sheriff Mills protect a girl who has escaped from a vampire nest.
- Affably Evil: Celia, the Evil Matriarch of the nest, acts kind and caring toward Alex. Doesn't stop her from emotionally manipulating the girl — or from killing people.
- A Day in the Limelight: For Sheriff Mills. Sam and Dean are almost minor characters.
- Continuity Nod: One of the vamps disposes of the evidence by feeding a victim's remains through a woodchipper.
- Defrosting Ice Queen: Alex may not have much regard for Jody's feelings (or for basic manners) at first, but she gradually warms up to her. The feeling's mutual.
- Do Not Taunt Cthulhu: "Did I help your shut-in kid sister get away from her weird, scary-ass squatter family? Answer's still no." Even if they weren't vamps, that's a terrible answer to give when said scary-ass family has you surrounded.
- Evil Cannot Comprehend Good: Celia doesn't understand why Alex would betray her to save Jody.
- Evil Counterpart: Celia to Sheriff Mills. Both have lost their children and consider Alex a substitute for the child.
- He Who Fights Monsters: In keeping with the past few episodes, Dean's becoming even more drawn to violence due to the Mark of Cain's influence. The man who had put "saving people" above "hunting things" now tells Jody that raiding the nest comes first, rescuing Alex comes second — unless Dean decides to kill her first. Sam raises the point that he seems to be enjoying the killing a little too much.
Dean: Killing things that need killing is kind of our job. Last I checked, taking pleasure in that's not a crime.
- Mama Bear: Jody. Celia too, in a far more twisted way.
"You callin' my family weird?"
- Pædo Hunt: Played with, as the vampire nest uses Alex to lure out bait, and due to her youth most of their victims are would-be pedophiles/rapists. They don't do this altruistically, but because they hope that the men who go after Alex won't be missed.
- Pre-Mortem One-Liner: "LOOK AT ME, BITCH!"
- Lampshaded a couple of scenes later. "Well hey, you got another snappy one-liner, I'm all ears."
- Replacement Goldfish: The reason why Alex got her name. Jody correctly guesses that Celia renamed Annie and refused to turn her because she had lost a daughter named Alex. Jody later admits to Sam and Dean that her judgment about Alex had been clouded due to similar feelings.
- The Schlub Pub Seduction Deduction: Alex's modus operandi for luring her family's dinner back to the nest. Not that the one guy shown in the flashback looked like an utter slob, but his lecherous behaviour reinforces the trope.
- Shout-Out: To The Walking Dead when Mills mentioned a deputy having nightmares after watching the barn scene.
- The title is one to Martha Marcy May Marlene, complete with a girl having escaped from a cult and struggling with the after-effects.
- Stockholm Syndrome: The episode starts shortly after Alex finally escapes from her vampire "family", and she's clearly terrified at the prospect of being caught and dragged back home. She's just as terrified of disappointing "Mama", the vamp who kidnapped her almost nine years before. Celia encourages it by telling Alex that no one outside the family can be trusted, especially not someone like Jody.
- Unwanted Rescue: Alex is ungrateful to Jody because the guy who was about to kill her was her brother.
- What the Hell, Hero?: Sam gives Dean a brief one over his overly gleeful, quippy ("Look at me, bitch!") slaying of the vampires.