A woman prepares dinner. Her husband returns home annoyed that he had to work late. She tells him that they have a party to go to over the weekend. He becomes angry that she said he would go. She tells him she'll cancel. She asks what's wrong with him because it seems like he wants to have a fight. He then begins to beat her.

Dean wakes up and hears Sam whispering on the phone. Sam hangs up and Dean pretends to still be asleep. Sam wakes Dean and tells him that a man in Iowa beat his wife to death with a meat tenderizer. Sam says another man killed his wife as well and neither one had a prior history of violence.

Sam and Dean meet with Mr. Benson in the jail. He tells them that he killed his wife because she made plans without asking him. Sam asks if he felt possessed. He says he knew exactly what he was doing. He says he doesn't know why he did it because he loved her and they were happy. Dean shows Mr. Benson his credit card bill and says he knows he visited a strip club. He admits that he was seeing a stripper named Jasmine that he met at his friend's bachelor party. He says she went up to him and he thought she was perfect, but can't explain exactly what it was about her that was so great. He says his wife never knew. He then says he killed his wife because Jasmine said they would be together forever. He says he was supposed to meet Jasmine after he killed his wife, but she never showed up. Sam asks if he told the cops and he says Jasmine didn't kill his wife, he did.

Sam meets with Dr. Cara Roberts and asks about the three cases of the men who killed their wives. She says she didn't find anything unusual with the wives. Sam asks about the husbands. She asks if she can see Sam's FBI badge again. He shows it to her then, she says all three men had oxytocin in their blood. She says it's a hormone that shows up in childbirth, lactation, and sex. She says it's called a love hormone. Dean walks in and starts to talk, but Sam cuts him off. Sam asks Cara what could have caused the levels of hormones in the men and she says nothing she knows of. Sam then recommends she have a greasy breakfast to cure her hangover. The brothers leave and Dean tells Sam he C blocked him.

Dean tells Sam about the girls at the strip club and how the men all talked about the women in the same way. Sam says he thinks the men could have been under a spell. Dean is excited that they get to work a case with strippers.

Dean asks the strip club owner about the three women, but he doesn't know anything about the women. He says they use fake names and get paid in cash. Sam tells Dean that he talked to Bobby and he thought it could be a siren. Sam says sirens can read minds and they can make themselves look like anything you want. Dean asks if the three women could have all been the same chick. Sam says yes. Meanwhile, a stripper named Belle takes a guy out of the bar. They go to his house and he tells her his mom is asleep. Belle tells him he is amazing, then takes off her clothes. The two have sex and Belle turns into a monster without the guy noticing. Afterward, Belle tells the guy that his mom takes up all his time. She says as long as she's around, they can't be happy. He tells her his mom is not so bad. She asks if he wants to be with her forever. She then tells him to bash his mother's brains in and he agrees. He gets up and pauses. She tells him she loves him and he grabs a fire poker and kills his mom. Belle then gets dressed and leaves.

Dean checks Sam's phone. He dials the last number Sam called and hears Ruby's voice. Sam walks into the room and tells Dean about Belle and the guy who killed his mom. Sam's phone rings and Dean says he forgot his cell phone. Bobby is on the phone. He says they need a bronze dagger to break the spell of the song. Sam asks when the siren injects the venom. Bobby says it could be during sex and Dean jokes that it's a supernatural STD. Bobby then says if the siren get a dose of their own venom, it will kill her. Bobby warns the guys to be careful.