Olivia Lowry, a Hunter, is sleeping on the couch when her TV switches to a blank channel and the air temperature drops. She goes to a hidden closet and takes out an EMF meter, and registers a massive reading of spiritual entity. Bobby calls on her answering machine but she's busy grabbing a gun and checking out her house. The ghost of a man appears before her. She draws back, clearly recognizing him, and then fires a round of salt. She starts to make a circle of salt but the man's spirit reforms. Olivia begs him for forgiveness and then hears someone behind her: a female ghost, who shoves her hand into Olivia's stomach.
Bobby and Dean bring Sam up to speed on their meeting with Castiel. Sam is impressed but Dean doesn’t believe Castiel is a demon. Bobby does some research and confirms that an angel can pull a soul out of Hell, but Dean is creeped out at why God has chosen a normal guy like him. Sam goes to get some food but meets with Ruby and tells her what's going on. She warns that angels are dangerous to her kind and show no mercy. She heads out and warns him to do the same.
When Sam returns, the trio head out to meet with Olivia. Bobby's been trying to call but she doesn't return her home. They go to her home and find her corpse, ripped to shreds. Bobby starts calling other Hunters in the area but has no luck. They split up to confirm that the Hunters are dead. As Dean and Sam head for Bobby's place, Sam stops at a gas station, fills up the Impala, and goes to wash his hands. As he's in the restroom, the temperature drops and a figure appears behind him: Special Agent Victor Henricksen. Henricksen blames Sam for his death and attacks Sam. The ghost gets the upper hand but Dean arrives and blows it away temporarily with rock salt so they can escape.
Bobby is at his house when the radio goes crazy and the temperature drops. He sees a ball bouncing down the stairs and turns to see two young twin girls, dressed in white.
Sam and dean arrive the next morning and find no sign of Bobby. They split up to search and Sam goes outside to check the junked cars. Inside, a door slams open by itself and Dean is confronted by Meg Masters: the host body of the demon that tried to kill them. She blames him for her death, saying he didn't try to free her from her demon possessor. She attacks him while blaming him for being too reckless and thinking he's a hero. Dean denies being any kind of hero, and notices a brand on her right hand.
Outside, Sam is searching the junkyard unaware that the two girls have Bobby in trunk and are tormenting him with descriptions of how he failed them. Sam notices the temperature dropping and realizes they're nearby. Inside, Meg heaps on the guilt and tells Dean that her sister killed herself out of grief after learning that Meg was dead.
Sam finds Bobby and together they drive off the twin ghosts using iron rods. Inside, Dean draws a normal pistol, which is useless against Meg..., but he shoots down the iron chandelier on top of her, temporarily dissipating her. The three men get together and Sam realizes he saw the same brand on Henricksen's hand. Before they can pursue the matter, the temperature starts dropping again. Bobby gets them into a cold-steel panic room in the basement where they prepare salt shells and do the research. While Dean wonders how God, if he exists, could let so many Hunters die, Bobby discovers that the brand is the Mark of the Witness. Someone or something summoned the vengeful dead using the Ritual of the Witnesses and turned them against those who were responsible for their deaths. The Ritual is one of the signs found in Revelations: an indicator of the Apocalypse.
Bobby finds the spell they need to send the ghosts back to their final reward. However, the components are scattered throughout the house. They load up and head for the stairs, only to find Ronald Resnick ("Nightshifter") waiting for them. He blames Dean for his death and they have no choice but to shoot him with rock salt. Bobby and Dean head for the library where there's a fireplace they need for the ritual. Sam goes upstairs and finds Meg waiting for him. She condemns him for working with Ruby, who has killed dozens of young girls for host bodies. He blasts her away... for the moment.
Dean goes to the kitchen to get the necessary herbs and the ghosts seal him off from Bobby. Henricksen appears to Dean and describes how Lilith didn't kill them... right away. Henricksen thrusts his hand into Dean's chest but Sam arrives in time to save his brother. They get back to the library and try to hold off the five angry spirits while Bobby completes the ritual. They start to run out of ammo and the ghost close in and overwhelm them. Meg attacks Bobby, who drops the bowl containing the components. Dean grabs it and throws the ingredients into the fire, sending the ghosts away in a burst of white light.
Later, Dean and the others are dozing but he wakes up to find Castiel in the kitchen. The angel congratulates Dean but admits he wasn't there because he was fighting another battle. Castiel then explains that the Ritual was one of the 66 Seals: if all the Seals are broken, Lucifer will walk the Earth once more. The angels are becoming involved on Earth to stop him at all costs, and have already taken heavy losses. When Dean snaps at him, Castiel warns that he can send Dean back to Hell as easily as he removed him. He disappears and Dean wakes up. The next morning as they prepare to leave, Dean questions Sam's belief in God... then notes that the existence of God must mean that Lucifer also exists. Share this article with your friends