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9 "Holy Terror" Thomas J. Wright Brad Buckner & Eugenie Ross-Leming December 3, 2013 4X5059 2.42[10]
A civil war starts between angels working for Bartholomew and angels working for Malachi, an anarchist, both of whom want to rule Heaven which will end in disaster. Sam and Dean initially investigate with Castiel, but Ezekiel makes Dean send Castiel away. Desperate, Castiel prays for help and is met by an angel named Muriel who is neutral in the war. Castiel convinces her to hear him out and she explains what she knows, but he is captured by Malachi and another angel named Theo who were tracking Muriel. Malachi tortures Castiel for information on Metatron, killing Muriel to try to force him to tell him what he knows. He reveals that many angels died in the Fall from Heaven, including Ezekiel. Malachi leaves Castiel alone with Theo who wants to defect to Metatron's side. Castiel tricks Theo into releasing him, then steals his grace, turning him back into an angel and at least partially restoring his powers. After escaping, Castiel calls Dean to warn him about "Ezekiel." At the same time, Metatron meets with "Ezekiel" who is revealed to really be the angel Gadreel who guarded the Garden of Eden until the Serpent got in and was disgraced. He was released by the Fall and Metatron proposes working together to restore Heaven with angels that they like (Metatron having grown bored with his solitary rule of Heaven). Gadreel is initially reluctant, but agrees and is given orders by Metatron to kill someone to prove his allegiance. After learning the truth from Castiel, Dean uses a sigil to knock Gadreel out so that he can tell Sam the truth, but "Sam" knocks him out and reveals himself to really be Gadreel, having altered the sigil so it gave him control rather than Sam. Gadreel kills Kevin and leaves, taking with him the angel and demon tablets, but leaves Dean alive to mourn the loss of Kevin and Sam.

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10 "Road Trip" Robert Singer Andrew Dabb January 14, 2014 4X5060 2.21[11]
While Dean grieves over the loss of Kevin, Gadreel is killing more targets given to him by Metatron. Dean fills Castiel in on Kevin's death and Sam's situation. Castiel informs Dean that they can bypass the angel and talk directly with Sam, who can then cast Gadreel out. They enlist the help of Crowley to find and capture Sam. As they are leaving, a lessor demon informs Abaddon of his whereabouts. One of Gadreel's targets is an old friend named Abner who explains that true happiness is getting what you want most in the world and holding on to it no matter the price. Gadreel kills Abner, but is captured by Dean and Castiel. After torturing Gadreel and trying to reach Sam, Gadreel claims that he has experienced far worse and has all the time in the world to wait until he is rescued. Dean strikes a deal with Crowley and promises to free him if he possesses Sam to wake him up. Crowley possesses Sam and succeeds and helps him cast Gadreel out. After re-possessing his old body Abaddon shows up and Crowley tells Dean, Sam and Castiel to leave through the back door. He talks with Abaddon and claims that he is still alive, kicking and will campaign to win Hell back. He disappears before Abaddon can start an actual fight with him. Dean tells Sam that he is going to hunt Gadreel alone as he is 'poison' and causes too much hurt to those around him. Hurt by Dean's trickery, Sam warns him that Gadreel is not their problem; he refuses to elaborate, instead bidding Dean to go.

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11 "First Born" John Badham Robbie Thompson January 21, 2014 4X5061 2.65[12]
Crowley approaches Dean for help with finding the First Blade, the weapon that the Archangels used to kill the Knights of Hell as it is the only thing that can kill Abaddon. Following clues, Dean and Crowley discover that John Winchester had once worked with a hunter named Tara who spent years searching for the blade. Finding Tara, they cast a locator spell she found that leads them to the biblical Cain (guest star Timothy Omundson), one of the first demons who trained the Knights and slaughtered them. Cain refuses to help and when a bunch of demons show up, he lets them in to fight Dean and Crowley who kill them. Cain reveals he killed Abel to keep him from working with Lucifer and allow him to go to Heaven and that he wants revenge on Abaddon as she murdered his wife. Cain finally reveals that the spell led them to him because the Mark of Cain he possesses is the source of the blade's power and he can transfer it to someone worthy such as Dean. Despite Cain's warnings of a terrible cost, Dean agrees. Cain asks for Dean to come back and kill him after killing Abaddon and sends him and Crowley to safety as an army of demons arrives to kill him. Dean realizes Crowley was using him, but still needs him as the blade is located at the bottom of the ocean and only Crowley can find it. At the same time, Castiel realizes that part of Gadreel's grace is still inside Sam and that they can use it to track the angel. Removing the grace causes Sam to start reverting back into the state he was before Gadreel possessed him, but Sam refuses to let him stop until they get all the grace they need even if it means his death. Realizing that he can't let Sam sacrifice himself and understanding his wish for redemption due to his brief humanity, Castiel stops and finishes healing Sam and eliminating the last of the grace. They try the spell but they didn't get enough grace. Castiel leaves to track Metatron who he believes holds the key to fixing everything.

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12 "Sharp Teeth" John Showalter Adam Glass January 28, 2014 4X5062 2.76[13]
After Garth (special guest star DJ Qualls) is hit by a car after mutilating a cow in Grantsburg, Wisconsin, Sam and Dean arrive separately to investigate where their friend has been for months. Claiming to remember nothing, Garth escapes the hospital and Sam and Dean follow him to discover that Garth is married to a werewolf and is now one himself after being bitten six months before on a hunt. Garth insists that he and his pack don't harm humans and peacefully coexist. While Sam is more willing to trust Garth, Dean isn't after his long disappearance and due to his suspicious nature. As everything seems to be fine, Sam and Dean are lured into a trap by the local sheriff who is also a werewolf and are forced to kill him when he attacks. Looking for Garth, Sam finds him and his wife Bess missing and is kidnapped by a few members of the pack while Dean finds out that they worship Fenris and believe that when Ragnarok comes, they will rule over mankind. The wife of the minister plans to murder Garth and Bess and frame Sam and Dean to goad the rest of the pack who is willing to live in peace into action, but Dean arrives and kills the three werewolves running the plot. In the aftermath, Garth offers to return to hunting using his new werewolf powers to help, but Dean tells him to enjoy his new life, having realized that all werewolves aren't so bad. Dean tries to make up with Sam who agrees to return to hunting with Dean, but doesn't fully trust him anymore.