|A Hunter, Olivia Lowry, is dozing off in front of her TV when it flickers. The room grows colder and she goes to the closet to get an EMF meter. After confirming large amounts of spirit activity, she gets a gun out of her arsenal. The phone rings and Bobby calls and leaves a message asking for help on her answering machine. Olivia turns and sees a dead man standing before her, a man she recognizes. She fires and it dissipates, giving her time to make a circle of salt. The dead man appears and she apologizes, and then turns to see a dead woman who thrusts her hand into Olivia's stomach.
Dean and Bobby meet with Sam and brief him on their encounter with Castiel. Dean doesn't believe Castiel is an angel but Sam is less skeptical. Bobby confirms that the research shows an angel can take a soul from Hell and admits that it seems likely God is involved. Dean wonders why God has chosen him when he's just a regular guy and admits he's creeped out. They start doing research on angels and Dean sends Sam out to get some food. Sam meets with Ruby, who wants to know if an angel is involved. When Sam confirms it, Ruby prepares to leave while warning that angels smite first and ask questions later. She doesn't know much about them except that they're dangerous to her kind.
Sam returns to find Bobby and Dean packing to check on Olivia, who hasn't returned her calls. They arrive at her house and find her corpse and an unbroken salt line. Bobby is unable to get hold of any other nearby Hunters and they figure something is up. Dean calls another Hunter, Jed… who is dead the same way. Dean and Sam confirm Jed's death while Bobby finds two other Hunters dead. They head for Bobby's place and stop for gas en route, unaware that someone is watching them. Sam refills and goes into the washroom while Dean sleeps in the Impala. Sam notices the temperature drop and turns to see the ghost of Special Agent Hendrickson behind him. The spirit explains that Hendrickson didn't survive and blames Sam for his death. He slams Sam around and throws him to the floor, but Dean arrives and dissipates him with rock salt.
Bobby is at his place when the temperature drops and the radio spews out static. Bobby takes a poker and goes hunting, and sees a ball bounce down the stairs. He turns to see the ghosts of two young twin girls. Sam and Dean head back for Bobby's house and arrive the next morning. They split up and Sam goes outside, unaware that Bobby is being held in a junked car. Inside, a door slams and Dean turns to confront the spirit of Meg Masters, the human host that the body possessed. She explains how she was a college girl possessed by the demon and conscious the entire time the demon murdered people. She's not thrilled that Dean had her thrown off a building and had hoped that he would help release her. She gets close enough to punch him, knocking him to the ground. She kicks him and then accuses him of getting her killed with his recklessness. As she grabs him, Dean notices a symbol on her right hand.
The two girls are holding Bobby in the car and blame him for not saving them, then start to smother him. Nearby, Sam notices the temperature drop and starts searching the junked cars. Meg blames Dean for her sister killing herself after discovering Meg was dead. Outside, Sam finds Bobby and the ghosts knock him back. He manages to dissipate one of them and Bobby sends away the other.
A battered Dean crawls away from Meg and draws a gun. She says she's immune to bullets but he shoots the iron chandelier above her. It falls down, dissipating her. They get together and compare notes, and Dean describes the mark on her hand. Sam saw the same mark on "Hendricksen's" hand and draws it. The temperature drops again and Bobby takes them to a ghost-proof panic room in the basement. The brothers prepare salt shells while Bobby researches the symbol. Dean wonders why God isn't involved and why people are suffering. Bobby explains that the symbol is the Mark of the Witness. Someone forced the ghost to rise and they exist in agony. The summoner was so powerful he left the mark on them. The ritual, the Rising of the Witnesses, figures into an ancient prophecy of Revelation: a sign of the Apocalypse.
Bobby has found a spell to send the spirits back to their final resting place but the components are outside in the house. They arm up and head out, and confront Ronald Resnick, who died fighting a shapeshifter. They start collecting components throughout the house and are forced to split up. The twin girls appear and Dean dissipates them and then sends Dean to the kitchen. The twin girls appear again and Bobby fires. Upstairs, Meg appears to Sam and talks about what he's doing with Ruby, who has killed dozens of innocent girls. Sam blows her away. Downstairs, the ghosts seal off Dean in the kitchen by closing the doors. Hendricksen confronts Dean and explains that it took him and the others 45 minutes to die when Lilith decided to torture them slowly for fun. Hendricksen thrust his hand into Dean's stomach but Sam arrives and dissipates the ghost just in time. They get back to the library and Ronald appears, but then disappears before Dean can shoot him. The windows burst open and the wind blows in, scattering the papers and the salt. The ghosts appear and Dean and Sam run through their ammunition holding them off. Finally they're out of ammo and Meg pins Dean against the wall and he uses an iron poker to hold off the spirits. The twin girls close in on Sam, while Meg thrusts her hand into Bobby's back. Dean just manages to catch the components and throw them into the fireplace, completing the ritual and sending the ghosts back to where they came.
Later, everyone is sleeping when Castiel appears to Dean. He congratulates Dean on their success and notes that he's not there to help Dean but to fight in a larger war. Dean wonders where God is and what he's waiting for. Castiel informs him the Rising of the Witnesses is one of the 66 Seals, which Lilith is breaking to bring on the Apocalypse. Castiel explains that the last Seal opens and Lucifer walks free upon the Earth. The angels walk the Earth to stop his summoning. Castiel warns Dean that he can throw him back into Hell as easily as he removed him… and disappears. Dean wakes up the next morning and is left to wonder if his conversation was a dream. He asks Sam about his belief in God and angels, and notes that Sam must also believe in the Devil.