The Winchesters are brought to town in pursuit of a grisly case. Men are being thrown so hard against walls they break them. Their hands and feet are cut off brutally. A bizarre symbol is etched into each of their chests, like a calling card for a serial killer. It's unusual enough to get Sam's attention, and since he's the one driving, that is where they will go next.
They arrive in Seattle and easily settle into routine, posing as FBI agents pursuing a serial killer. Upon talking to the forensics officer, they learn that the flesh found in one of the victim's mouths is an anomaly itself. Dean, who would rather pursue Dick Roman, tries to blow this case off, but Sam quips, "Yeah, uh, "didn"™t match anything human" usually seals the deal for me."
Sam has buried himself in work for awhile now. This episode's monster may not be connected to him as so many have been in the past, but his story shines in this as well. He has thrown himself into the hunt, always moving, always ready for the next case. He cannot stop, or he will find himself facing his own demons.
Much like his brother, he will not talk about or acknowledge the issues that plague him. He may have owned up to them when necessary, but he has taken to avoiding them at all costs. He runs, he works, he hunts, he researches---and lately he drives. Anything to chase off and out run the hallucinations that lay beyond the fringes of his consciousness. It's fascinating how, as an undercurrent, Sam's storyline runs through it like a dark thread.
He expresses frustration, hides his need to work from Dean in quips, such as, "Dude, you're obsessed," or "she gave you her number?" Sam may have fessed to his hallucinations, but he feels that he must not burden his brother. So, he works. He chases down the evidence at the forensics lab, talks to the professor, and handles the leg work for much of the basics of the case---all while Dean is caught up in the middle of it.
Essentially, Sam has learned that if he stops moving, he dies. The search for Dick Roman, or any weakness he may have has gone cold, and therefore a determent to Sam's outpacing of his nightmares. It's not much different than Dean's handling of Hell in season 4, a marathon of hunts that string them both out and test tempers.
While Sam is left to research, Dean heads off to the bar. Unlike his difficulties in "Defending Your Life," he lies smoothly and picks up Lydia. They head back to her place and spattered amongst their sex scene are cuts to another victim meeting his untimely end.
Dean, unknowingly, has slept with one of the Amazon women---the very thing they are hunting.
Dean possesses Bobby's flask and holds it dear. He, however, forgets it at Lydia's, and has to go back and retrieve it. A ho hum case for Dean suddenly becomes extremely personal as he enters her home and finds that the woman he spent the night with has a young child. What's even more disturbing is that it seems that this child can speak like an adult. Instantly, Dean's hunter radar goes off, and he focuses on trying to figure out more about Emma.
Emma's short life---a mere three days---reflects Dean's life through a strange prism.
She has no childhood, becomes motherless, endures painful training, and is forced to kill her own father in order to live and become a full member of her tribe. Her death, is also an echo of Dean's.
Emma, due to her monster nature, has no childhood. She will be an adult in a short three day period. While Dean himself is not a monster, nor did he endure such a rapid growth, he too had to become an adult rapidly. He lost his childhood the moment his mother was killed by Azazel and John thrust a baby Sam into his arms. At the tender age of four, he shouldered responsibility for his little brother and the life in a single instant.
As Dean watches over Lydia's house, he watches in shock as a little girl, no longer a baby, is handed from Lydia to two women. The little girl's name is Emma, the same as the baby he saw in the play pen a few hours earlier. He follows them to a building, where Emma is let out and disappears inside. Upon return to Sam, he explains what he saw.
In Emma's scenes, we see her and other girls in a room with two women. One of them is the same woman Dean saw take a then five year old Emma away from Lydia. She states, "On this special night, you join an exceptional family. You are ready to take your places alongside us and learn our traditions."
They are forced to eat a tribute piece of flesh, drink some milk, and most of all, endure a branding that marks them as members of the Amazon tribe. It is their training prior to completing their blood sacrifice and entrance into full adulthood.
It may be brief, but it is a stark reminder of Dean's own upbringing under John. We know that he was aware of hunting and what their father did at a much younger age than Sam. He had to in order to protect his little brother while John went on hunts.
Emma, as she flinches from the brand, is told, "Fight it, Emma. As with all you do, courage is everything.
Dean has often buried his own pain---physical or mental---so that he may finish the current hunt or protect Sam and others.
It isn't until Emma arrives to kill Dean that we learn just how much she reflects him. In her pleadings, she speaks falsehoods about herself, but truths about Dean. The dialogue has taken all of the things he's hiding from"”-childhood, hunting, training, even Hell, and thrusting them into his face in a simple statement: "They stick you in there, and you trust them. It's all you know. And you don't question what they want you to do "“ terrible things. That's why I had to leave. They tortured me."
And yet, they are also falsehoods about Dean---they are the lies he tells himself.
Emma's death also reflects Dean's deal in a startling way.