The boys arrive in Chicago to investigate recent violent deaths. Disguised as operators from a security alarm company, they visit the apartment of the last victim, Meredith, who was ripped to pieces as if by a wild animal. They discount werewolves due to it being the wrong time of the lunar cycle, and struggle to find clues until Dean notices that the blood spatter on the carpet forms a symbol.

That night they visit the bar where Meredith worked. Sam has had no luck researching the symbol, and Dean chats to a bartender, but doesn’t gain any useful information other than her phone number. Suddenly Sam spots a familiar face; Meg, the girl he met when he left Dean and was going to travel to California to find John.

Sam is suspicious that her appearance is not a coincidence and decides to follow her while Dean checks out her background. While Sam sits outside her apartment, observing her from the Impala, Dean calls to say her story checks out, and that he has found out, with some help from Caleb, the meaning behind the symbol in Meredith’s apartment. It is a sigil for a Daeva, a type of Zoroastrian demon. Sam tracks Meg to an abandoned warehouse, where he observes her at an altar, communicating with someone through a goblet of blood.

Sam returns to tell Dean what he’s seen. Dean has his own information – both victims so far were actually born in Lawrence, Kansas. Suspecting that they may be close to the demon that killed their mother, Dean calls John and asks him to come to Chicago. The boys prepare to do battle, and Sam fantasies about what life may be like after they kill the demon. Dean reacts strongly when Sam expresses a desire to return to college, and opens up about his desire for them to be together as a family again.

At the abandoned warehouse, the boys’ plans are thwarted when Meg commands to daevas to attack them. Once they are restrained, bound to pylons, Meg reveals the murders were a plan to trap them, and use them as bait for John. The boys manage to distract her long enough for Sam to cut himself loose and overpower her and then overturn the altar. Freed from her control the daevas turn on Meg, and throw her from the window. Sam and Dean see her dead on the pavement beneath.

Returning to their room, Sam and Dean find an unexpected visitor – John. Their reunion is interrupted when the daevas attack them, slashing and beating them until Sam repels them by lighting flares.

Escaping outside to the Impala, Dean announces that Meg was right, John is vulnerable when he is around them, and they must separate. Sam protests, but John agrees. As they go their separate ways, they are observed by a figure in the shadows – Meg.

Information from Super-Wiki