Sam and Dean find three small town men have beaten their wives to death. Behind the murders is a siren, who puts the brothers under her spell and pits them against each other.

Sam and Dean enter a small town in Iowa, where three men have inexplicably beaten their wives to death. The brothers realize that behind the murders is a siren, a creature that can take different forms, desperately needs love and compels people to destroy themselves as a show of devotion. The siren eventually puts Sam and Dean under her spell and pits the two brothers against each other in a fight to the death.