Dean is desperate to hear from his father, but as he makes another call, Meg answers John's phone. Meg taunts Dean that John is beyond help. Sam responds by saying that they should find the Demon and kill it with the Colt, but Dean counters that they need a plan because John isn't dead.
The boys arrive at the home of another hunter, Bobby and their shared history is quickly sketched out - Dean seems to know him quite well, Sam not so much, and Bobby once ran John off with a shotgun. Sam goes through some of Bobby's books on demon lore, including the Key of Solomon, while Bobby and Dean talk. Suddenly Meg kicks in the door, attacks the boys, and demands the Colt. However, she soon gets caught under a devil's trap that is painted on the ceiling. Bobby explains that Meg is actually a girl possessed by a demon, and that the injuries she previously sustained in Chicago (in the episode Shadow) will kill her if the demon leaves her body. Dean insists on exorcising the demon to save the girl, no matter how broken she is. Sam reluctantly reads the ritual while Dean questions Meg about John; she repeatedly claims that John is dead. Finally, the demon is banished, and human Meg, dying painfully, thanks them and offers the clue "sunrise." The boys leave Bobby to head to Jefferson City.
On their way to rescue John, they boys argue about the importance of killing the Demon (Sam) and the importance of family (Dean). Dean says Sam is like John: eager to die if it means killing the Demon. They arrive at the building where John is being kept, form a plan to evacuate it that involves dressing up as firemen, and execute it. They manage to overpower the possessed humans guarding John and get him out of the apartment - after Sam insists on testing John with holy water. John is barely coherent, but he manages to ask about the Colt. Once all three are out of the building, they're set upon by Tom, who beats Sam severely. Dean whips out the concealed Colt and shoots him through the head.
In a secluded cabin, as the boys salt the doors and windows, Dean confesses that he's scared of the lengths he'll go to in order to protect his family. John enters, claiming that Dean should be proud of what he does for the family. Dean grows suspicious of the kind words and points the Colt at John. Sam allies himself with Dean, and John is revealed to be possessed by the Demon as his eyes glow yellow. The Demon injures both boys and taunts Sam's unreliable special powers, and he also mentions that Sam was about to propose to Jessica. Dean draws the Demon's attention away from Sam, and it reveals that the demons in Meg and Tom that Dean shot were his children. He uses some psychic power to attack Dean, causing him to bleed internally. Dean begs for his life, and John manages to surface long enough for Sam to free himself and grab the Colt. John begs Sam to kill him in order to kill the Demon while Dean pleads for Sam not to shoot. Sam uses the penultimate bullet in the Colt to shoot John in the leg, forcing the Demon to leave John's body.
Sam drives the Impala with John in the passenger seat and Dean, gravely hurt, in the backseat. John expresses disappointment that Sam didn't shoot and end the family's quest, but Sam says that killing the Demon is not the most important thing. Sam promises to get them to the hospital, but a huge truck slams into the Impala, smashing it and rendering all three Winchesters unconscious. The truck driver has the black eyes of the possessed.