Sam and Dean head to Bedford, Iowa, posing as FBI agents to investigate the murder of a woman whose head was smashed by a meat tenderizer by her beloved husband, Adam Benson. They discover three similar cases; a Dr. Cara Roberts explains that the three husbands had anomaly in their blood work, with the presence of Oxytocin, a love hormone. The Winchesters call Bobby and conclude that a siren might be casting a love spell. Bobby advises them to get a blood sample to revert the spell. Sam stays with Dr. Roberts to collect the samples. Meanwhile, FBI Agent Nick Monroe arrives to investigate and discloses to Dean that in all the crime scenes there was the Mediterranean plant, hyacinth. Dean recalls seeing the plants in Dr. Roberts' office and calls Sam; however, his brother is having sex with the prime suspect. Dean teams up with Nick to chase Dr. Roberts.
—Claudio Carvalho, Rio de Janeiro, Brazil