Millennia in the past, the Grigori were some of the first angels on Earth, assigned to watch over humanity. However, the Grigori went bad and the other angels attempted to wipe them out. While the angels believed they had succeeded, some of the Grigori survived in secret and began feeding on human souls.
In 2009, after the angel Castiel takes her husband Jimmy as his vessel for a second time, Amelia Novak begins a search for Castiel and her husband by investigating stories of miracles. To do this, Amelia leaves her daughter Claire with Claire's grandmother and spends the next four years searching. In 2013, Amelia's search leads her to a faith healer named Peter Holloway in Tulsa, Oklahoma. Unknown to her, Holloway is really the Grigori Tamiel who uses a man he healed named Ronnie Cartwright to find him victims in the form of people who won't be missed and bring them to him. Amelia falls victim to Tamiel's scheme and spends the next two years as his prisoner with Tamiel feeding on her soul.
After an encounter with the husband of the vessel of the angel Hannah, Castiel grows interested in the family of his own vessel and locates Claire in a group home where she ended up after being bounced around following her grandmother's death shortly after Amelia was kidnapped by Tamiel. During this time, Claire learns of her father's death and loses her surrogate father Randy to a Mark of Cain enraged Dean Winchester. Claire briefly tries to have Dean killed before making peace with Castiel and heading off on her own. While meeting with Castiel for the first time, Claire claims to him that Amelia had left to "find herself" following Jimmy's second possession and never returned. Once on her own, Claire decides to track down her mother, believing that Amelia had abandoned her.
Following Amelia's disappearance, the motel manager where she was staying sent her things to Amelia's last known address, including Amelia's diary which contained information on her search for Castiel. As Amelia no longer lived there, Amelia's things bounced from place to place before eventually finding their way to Claire at one of her foster homes. Using Amelia's diary and the last postcard sent to her, Claire tracks Amelia's last known location to Tulsa, Oklahoma where the diary talks about Amelia's plans to meet with Ronnie Cartwright. Claire is able to find Ronnie at Susie's Bar in Tulsa and questions him about Amelia. Ronnie claims to have no idea who Amelia is despite her diary stating that he was going to take her to "some miracle worker" and is unmoved even when Claire tells him that Amelia is her mother. Ronnie finally leaves the bar followed by a persistent Claire and slips up when he tells Claire he doesn't know Amelia Novak as Claire had never given him Amelia's last name. When Claire tries to stop Ronnie from leaving, he accidentally shoves her into a dumpster, knocking her out. Ronnie then calls 911 for her before running off.
After Claire is taken to the hospital, the police find Castiel's phone number in her cell phone's emergency contacts list and call him and Castiel calls in the Winchesters for backup for dealing with Claire. While Claire tries to get the three to leave, they refuse and question her on why she was at Susie's bar until Claire gives in and explains that she was looking for her mother who disappeared two years ago and Amelia's diary mentioned her planning to meet with Ronnie before her disappearance. Claire tells the Winchesters and Castiel that Ronnie knew her mother's name and thus knows something about her. After Claire states that Amelia was looking for miracles, Castiel questions why and Claire explains how Amelia was looking for him.
The Winchesters and Castiel step out of the room to discuss the situation with Castiel blaming himself for Amelia's disappearance due to her search for him. While Sam isn't sure if its something they need to investigate, Dean suggests that it could be since Amelia disappeared while hunting for an angel and shows signs of increased aggression from the Mark of Cain. Dean decides to have them question Ronnie themselves but when they go to tell Claire, they find her gone. In response, Sam decides to go to the motel where Claire is staying to look for her while Dean and Castiel question Ronnie.
At the bar, Dean and Castiel find Ronnie who tries to run before being stopped by Dean. Growing aggressive, Dean slams Ronnie's head down into the bar table when he calls Claire a bitch and again when Ronnie refuses to talk about Amelia. Ronnie finally talks, telling them that he worked for a faith healer who was the real deal and healed his blindness. Ronnie explains that after the healer, Peter Holloway, gave him his sight back, Ronnie went to work for him as payment, bringing him candidates who were young but lost and wouldn't be missed with Amelia being the last of these candidates. Some of the people Ronnie brought him Holloway healed, but others Ronnie noticed him tying up and cutting them which caused Ronnie to quit working for him. Having gotten all that Ronnie knows, Dean and Castiel depart while Ronnie tries to call Tamiel to give him a heads-up that hunters are looking for him.
Sam is able to locate Claire's motel room and gets there first, surprising Claire when she arrives. Sam insists that they are just trying to help her, but Claire doesn't want their help and when Sam asks, explains that while Amelia's diary was "mostly empty promises and regret", it had enough clues to get her there. While Claire continues to believe Amelia had abandoned her, Sam shows her the last postcard from Amelia where she talks about them being home soon and how that doesn't sound like she was planning on abandoning her. Sam asks if Claire checked Amelia's credit cards for clues, but Claire admits that she couldn't get the credit card company to send her her mother's records. Sam offers to teach Claire how to hack into her mother's credit card records as they could possibly give her a clue to her mother's whereabouts and Claire reluctantly agrees to stay long enough for Sam to show her.
Outside of Susie's bar, Ronnie is able to contact Tamiel and warns him that hunters are apparently after him. Tamiel recognizes this fact and appears behind Ronnie who insists that he was just trying to give Tamiel a heads-up. Tamiel is enraged as he wouldn't have needed a heads-up if Ronnie hadn't talked and blinds Ronnie before killing him with his angel sword.
Sam and Claire successfully hack into Amelia's credit card records just before Dean and Castiel return and inform them of what Ronnie told them. While they suspect that "Holloway" might be an angel, they are confused by the fact that he's healed some people and apparently fed off of others. Sam begins to look into the name Peter Holloway when he finds an alert from the local police about Ronnie's murder. After Dean's overaggressive behavior with Ronnie is revealed, Dean decides to check out the body with Castiel and Claire tagging along. Sam stays behind to continue looking into Holloway and Castiel informs him that the Mark's influence on Dean is worsening.
Dean, Castiel and Claire arrive at the crime scene with Castiel and Dean disguised as FBI agents and Claire as Dean's daughter. Looking over Ronnie's body, Dean notices the marks made by the hilt of Tamiel's sword which confuses him while the local sheriff tells them that Ronnie had made two calls just before his death to a number that is no longer in service. After the sheriff leaves, Castiel tells Dean and Claire that the wound looks like that of an angel blade but wider and he can't explain the strange markings.
Returning to the motel room, the group is informed by Sam that he has found a lead on Tamiel: county records show Peter Holloway owning a farmhouse thirty to forty miles outside of town with Amelia's credit card records indicating that she was staking it out. Knowing that Ronnie probably tipped Tamiel off and he is about to flee, Sam and Castiel decide to go after him but make Dean and Claire stay behind, Claire for her own safety and Dean to keep the Mark in check by keeping him out of a potentially volatile situation.
While Castiel and Sam are away, Dean and Claire bond over a game of mini-golf and seeing the marks the handle of the golf putter leaves when dropped all the way down a hole causes Dean to realize that the wound that killed Ronnie might've been made by an angel sword instead of an angel blade. Joined by Claire, Dean looks through the lore for angels who wield angel swords instead of angel blades and Claire finds the Grigori which Dean recognizes is a type of angel that the lore portrays as sometimes protecting humans and other times preying on them. The two realize that "Holloway" is a Grigori and when they are unable to reach Sam or Castiel, Dean decides to go after them. Rather than leave Claire behind, Dean arms her with a gun and allows Claire to join him.
Reaching Tamiel's farm, Castiel and Sam split up with Sam taking the farmhouse and Castiel the barn. Searching through the barn, Castiel locates the room holding Amelia and Tamiel's other victims and frees Amelia from her bonds. Amelia wakes up and attacks Castiel briefly, enraged about him taking her husband from her before calming down. After Amelia calms down, Castiel attempts to heal the damage Tamiel did to her without success, surprising him. Amelia tells Castiel about her dream life with Jimmy that Tamiel had put her into and realizes that Jimmy is no longer within Castiel. Castiel admits that Jimmy is dead and in Heaven and apologizes to Amelia for breaking his promise to Jimmy to protect his family. However, Amelia tells him that as long as Claire is safe he kept his promise and breaks down in tears about leaving Claire as she did. Castiel then examines Tamiel's other victims but can't determine if they are alive or dead and tells the horrified Amelia that she has been trapped for two years when she asks.
As Castiel finds Amelia in the barn, Sam searches the farmhouse and as Dean calls him to warn Sam about Tamiel being a Grigori, Tamiel ambushes Sam and knocks him out, handcuffing him to a chair. After Sam wakes up, Tamiel properly introduces himself and explains how he has been feeding on human souls since the dawn of man and sees the other angels as failures as they protect humanity rather than prey on them. Tamiel eventually leaves Sam alone and disappears while Sam uses a nail from the chair he is handcuffed to to pick the lock on his handcuffs.
As Castiel helps Amelia and Sam talks to Tamiel, Dean and Claire arrive and enter the barn where they are greeted by Castiel. Castiel leads the two to Amelia where she and Claire are finally reunited after years apart. As mother and daughter embrace, Dean orders them to stay where they are while he and Castiel go find Sam. Searching the house they find Sam who has managed to free himself but no sign of Tamiel. Dean and Sam update each other on the threat, as Castiel is shocked when he finds out that Tamiel is a Grigori as he had believed the Grigori to be long-extinct and questions where the abomination is. The three realize that Tamiel is in the barn when Sam tells them that he couldn't find him in the house.
In the barn, Claire tries to help the extremely weak Amelia to safety when they are confronted by Tamiel who tells Claire that there is no fixing Amelia. Claire shoots Tamiel four times with the gun Dean gave her but Tamiel is completely unharmed and taunts Claire that a gun can't harm an angel. Tamiel moves to kill Claire with his angel sword, but Amelia jumps in front of the blow and is mortally wounded.
Before Tamiel can attack Claire again, Dean, Sam and Castiel rush in and Castiel tackles Tamiel, knocking his angel sword from his hand. Castiel draws his angel blade, but Tamiel proves stronger than the Seraphim and knocks Castiel off of him. The Winchesters then attack Tamiel next with Sam restraining him while Dean attacks directly. However, Tamiel quickly breaks free and knocks them both to the ground. As Sam continues to fight Tamiel weaponless, Dean retrieves Castiel's angel blade and attempts to use it on Tamiel to no effect and both he and Sam are knocked to the ground. Castiel then attempts to attack Tamiel again but is easily taken down as well. As Tamiel goes to kill Castiel with his own angel blade, Claire retrieves Tamiel's angel sword and stabs the off-guard angel through the back with it, killing Tamiel. However, when Claire goes back to her mother's side, she finds that Amelia has died of her wounds.
Following Amelia's death, her soul goes to Heaven where she is finally reunited with Jimmy. With Claire having no family left, the Winchesters and Castiel decide to send her to Jody Mills until she can get on her feet. The experience causes Claire to show an interest in hunting, causing Dean to leave her a lore book on angels in case she decides to become a hunter herself.
- Claire killing Tamiel is one of the few times on the show that an angel has been killed by a human rather than another angel.
- After Claire kills Tamiel, she takes his angel sword for her own. In Don't You Forget About Me, Claire is shown to still have the sword and uses it in her efforts to be a hunter.
- Claire's experiences with the Winchesters and Castiel while trying to rescue her mother give her a new perspective on what they do and causes her to make peace with Dean and Castiel, both of whom she had issues with for the death of her father and the destruction of her family.
- The fight with Tamiel is the first appearance of an angel sword rather than an angel blade.
- The fate of Tamiel's other victims are unrevealed following his and Amelia's deaths. Castiel was shown to be unable to tell if they were alive or not, but Tamiel stated that Amelia, who had been his victim the shortest, couldn't be saved. Presumably his other victims were already dead or died later on.