Sam and Dan get called to Sioux Falls by Sheriff Jody Mills, after she cuts off the head of a vampire who was following a runaway. The runaway, a girl abducted eight years ago, insists her name is Alex, when her DNA says her name is Annie. Alex has scar build up on her neck from vampire feedings, meaning she was a blood slave. And since she’s been with the vampires for eight years, she’s not willing to give up the location of her “family’s” nest, even though she ran away.
The boys are able to figure out a rough area of where the nest is located thanks to a bus ticket. While they go to scout out locations, Jody takes Alex up to her family’s cabin which brings up some memories of the family the sheriff lost.
Sam and Dean find one of the vampires at a wood chipper, using it to get rid of the bodies of earlier meals. They capture and interrogate the man, who tells them Momma never turned Alex and that she acted as a delivery person for them. She would lure men from the bars using the name Ann and bring them home for the vampires to feed on. The boys call Jody to let her know about Alex, but the rest of the vampires have already arrived at the cabin. By the time the Winchesters get there, Alex is gone and Jody is unconscious.
Jody insists on coming with the boys to go after the vampires. They let her but they warn her this is not a recovery mission; their priority is to clean out the vampires and they are not worried about Alex. Jody agrees but still goes into the nest and looks for Alex. When she finds her, she discovers Alex has been turned and is ambushed by Momma.
In the other room, Dean is knocked out by a vampire and Sam is tied to a chair, being drained of his blood for a “snack for the road.” When they are almost done with Sam, they go to prepare Dean, who has been pretending to be unconscious. The second the vamp comes near him he injects him with dead man’s blood and cuts the others head off.
Alex is trying to convince Momma to let the sheriff go, but Momma still wants to kill her, saying Jody is using Alex to fill a hole in her life. Jody accuses Momma of the same thing, after realizing why she changed Annie’s name to Alex; it was the name of her real daughter. Angered, Momma goes to bite the sheriff but Alex injects her with dead man’s blood before she can harm the sheriff. Sam and Dean reach them just as the sheriff cuts off Momma’s head.
They give Alex the cure used on Dean in a previous episode to change her back to human and Jody admits she used bad judgment during this hunt. She had been burying the grief under work and other things, but at least she can understand what Alex is going through and try to help her. She says her goodbyes to the boys and goes to check on Alex.
Now that they’re alone, Sam talks to Dean about the pleasure he took in killing those vamps and how he’s starting to change, more than likely due to the mark of Cain. But Dean just responds, "Killing things that need killing is kind of our job. Last I checked, taking pleasure in that is not a crime."