After their brief hiatus, the Winchester brothers are back to carry on saving the world from the monsters that go bump in the night. This week, a poor unsuspecting man finds himself tossed across his home and butchered with a knife. His hands and feet were cut off, and a demonic symbol was carved into his chest.
This news quickly reaches Dean and Sam, who thinks that a regular hunt would be a good change from the endless hunt for Leviathans. Several other men have been found similarly slaughtered, so they head off to investigate. At the morgue, they get the first clue in DNA found in the mouth of one of the victims. He tried to bite his attacker, but the DNA is not even slightly human.
Sam is all ready to head to their hotel for old fashioned research, but Dean has his own methods. He goes undercover at a local bar, where he soon finds himself with a beautiful woman, played by The Vampire Diaries' Sarah Canning.
They don't stay in the bar long, and are soon back at Lydia's place. It would seem to be a normal hookup for Dean, but the scene is mirrored with another supernatural killing.
The next morning, Dean is recovering from his fun night while going to the next crime scene. Sam also doesn't have any leads concerning the strange symbol carved into the men's chests.
Dean is a little distracted, having discovered that he left Bobby's flask at Lydia's house. When he calls her to ask about it, she is dismissive of him. After she hangs up, Lydia looks down and we can see that she is now extremely pregnant. To make it all more suspicious, she soon goes into labor in a candlelit room surrounded by blank-faced women.
To find out more about the strange symbol, Dean and Sam visit a local college's anthropology department. The professor identifies it as an ancient symbol distorted for worship, but can't do more than that on such short notice. They are lost without Bobby, but have to settle for whatever they can find.
Frustrated, Dean heads over to Lydia's to get his flask. She is still dismissive, but can't hide her baby. However, it's not the newborn we saw earlier. The baby girl has grown quite a lot and is talking with full complete sentences. This fact, Dean cannot help but hear.
Returning to the morgue, Sam notices a similarity of all the dead men. Every single one of them visited the same bar where Dean met Lydia. Dean is also sensing that there is more to Lydia, and he is outside tailing her. He sees two of the women who were there during Lydia's labor. A few minutes later they leave with the child, who is no longer a baby but a little girl.
Dean continues tailing them, down a dark alley. He goes back to report to Sam, who brushes off the strange child. At the same time, the girl is not only older but joined by several other girls in a strange ritual. The leader of these women tells the girls that they are honored to be hunting for the one who protects them. The killings Dean and Sam are investigating are blood missions.
The professor has identified the symbol carved into the victims. It's a symbol of the Amazons. This tribe of warrior women would use men for sex, and then kill them once they were pregnant. Everything matches up with the current cases, and so now the brothers know what to hunt.
However, the Amazons are onto them. One is the head detective on the murders, and, according to her boss, both Sam and Dean will soon be taken care of.
Sam and Dean are back to researching and Sam takes on his role of explaining the lore. He explains the strange growth of the child, and this upsets Dean. The child he watched grow up is quite possibly his. Despite now being a father, he is scheduled to die soon.
Back at the Amazon headquarters, all the girls are now young women being branded and sent out for their final mission. Still researching, Dean notices that their papers are being moved. Ever suspicious, Dean's mind wanders to the thought of Bobby's ghost. Still, Sam takes the moving page to the professor to translate the Greek.
Left on his own, Dean hears a knock at the hotel door. He stupidly opens the door, and his daughter is standing before him and asking for him. She says she ran away from the Amazons to escape their way of life. Dean buys the story and lets the girl into the hotel room. He listens to her beg for a normal life, but can't help but feel awkward with the whole situation.
Sam is still with the professor, who is more interested in how the paper was made than what is written on it. Yet when he does translate it, he tells Sam that it is the children who must kill their fathers. Before he can call Dean, the detective arrives to cut him off. She tries to fight him, but Sam shoots her point blank.
But Dean isn't defenseless either, and pulls a gun out as he gets his daughter's knife. He was expecting all this, but can't pull the trigger just yet. However, Sam doesn't have the same hesitation about killing his niece.
After seeing that their headquarters is empty, Sam and Dean leave town. Sam is concerned for his brother, seeing that he no longer has his head on straight. Dean almost died because he hesitated, but he doesn't see that as a problem.