After rescuing the Seraphim Castiel from Purgatory, the angel Naomi places him under her control to use as a spy against the Winchesters. Naomi eventually sends Castiel, with the help of the Winchesters, to rescue the captured angel Samandriel from the King of Hell Crowley. With the help of the Winchesters, Castiel successfully rescues Samandriel, but not before Samandriel reveals the existence of an angel tablet to Crowley. As a result, Naomi forces Castiel to kill Samandriel and explains to him that the angel tablet represents a very grave threat to angels in the wrong hands.
After brainwashing Castiel to be loyal to her to the point that he is willing to kill Dean Winchester, Naomi sends Castiel on a Hunt for the Angel Tablet. Castiel's actions draw the attention of the Winchesters who join Castiel in his search alongside the demon Meg. Castiel eventually locates the angel tablet and nearly kills Dean under Naomi's control. However, touching the angel tablet severs Naomi's link to Castiel and frees him from her control. Castiel then departs with the angel tablet, stating that he must protect it from everyone, including his friends the Winchesters. Desperate to get their hands on the angel tablet, both the angels and the demons begin hunting for it and for Castiel.
As a tactic to avoid being found, Castiel began moving between the various Biggerson's in the country, disappearing from one and going to the next when the angels get close. Castiel primarily traveled between the Santa Fe, New Mexico, Palm Bay, Florida, Denver, Colorado, Pittsburgh, Pennsylvania, Portland, Oregon, St. Louis, Missouri, Bangor, Maine, Lincoln, Nebraska and Reno, Nevada Biggerson's. The angel Ion compares Castiel's tactic to trapping the angels following him in a quantum superposition due to the exactness of all of the Biggerson's restaurants.
After Ion and Esper fail to catch Castiel at the Santa Fe Biggerson's, Ion reports in to Naomi about their search for Castiel. After Ion explains the difficulties in catching Castiel due to the amount of Biggerson's he is moving through, Naomi decides to force Castiel to stop since they can't catch up with him.
After moving through the Bangor, Lincoln and Reno Biggerson's, Castiel returns to Santa Fe to find that all of the staff and customers are dead aside from Kara. Kara, her eyes burned out of their sockets, keeps repeating "they said you had to stop" as Castiel goes to help her. As Castiel moves to heal Kara, Ion and Esper appear with angel blades drawn. Ion holds his angel blade to Castiel's throat while Castiel is distracted with Kara, capturing him.
Once Castiel is in the angels' custody, Naomi comes to Earth to deal with him personally. Annoyed at Kara's continued crying, Naomi telekinetically snaps Kara's neck with a snap of her fingers. "We were supposed to be their sheppard's, not their murderers," Castiel states to Naomi. Naomi tells him "not always angel" and reminds Castiel of the day in Ancient Egypt when the angels slaughtered every first born infant whose door wasn't splashed with lamb's blood. Naomi calls that event "only PR." Naomi reveals that Castiel was there that day, but he just doesn't remember it. When Castiel questions how many times Naomi has wiped his memory clean of events, she admits that its been "too damn many." Naomi calls Castiel "the famous spanner in the works" who has never done what he's been told, "not completely" and he can't even die right.
Naomi demands the location of the angel tablet, but Castiel simply tells her "in the words of a good friend: bite me." Naomi tells Castiel that they will bite and orders Ion to search all of the Biggerson's. Naomi figures that Castiel must've hidden the angel tablet along the way somewhere.
As Ion searches, Esper beats Castiel who refuses to talk. Ion returns with the news that he has been all over, but the angel tablet is not there. Naomi tries to convince Castiel to give up the location of the tablet so that they can put it back in its rightful place, but Castiel feels that he must protect it "from all of us." "I'm just going to have to pull you apart, aren't I?" asks Naomi.
Suddenly, Crowley appears and shoots Esper through the throat from behind and shoots Ion in the arm, killing Esper and wounding Ion. Showing Naomi his gun, Crowley explains that he had one of his R&D people melt an angel blade down into angel-killing bullets which work just as well as the blades. Naomi is enraged by Crowley's audacity, but Crowley simply calls himself "the daringest devil you've ever met, love." Naomi begins to shine with holy white light, preparing to blast Crowley. However, Crowley takes aim at Naomi and reminds her of the last time she tried that. "Let's see who blinks first," Crowley challenges. Crowley shoots at Naomi who teleports away before the bullet can hit her.
Crowley turns his attention to Castiel who realizes that Ion is working for Crowley stating that "its that kind of universe these days." Crowley shoots Castiel in the gut and orders Ion to grab Castiel and follow him.
Taking Castiel to his office, Crowley states that he wanted to take some time to "chat" with his old business partner. Crowley assumes that they will have time since it takes a long time to bleed out from the gut. While Castiel refuses to tell Crowley where he buried the angel tablet, Crowley tells him that "luckily, I don't believe you'll have to." Crowley states that he has been getting regular updates from Ion who has told him that Naomi thinks that Castiel touching the angel tablet has broken her hold over him. Castiel insists that the tablets weren't meant for the angels or for Crowley.
Crowley tells Castiel of an epiphany he has had about the location of the angel tablet, feeling that Naomi has been too busy to realize it. Crowley has realized that if touching the angel tablet broke Naomi's hold over Castiel, why would he stop touching it? As Ion watches on uncomfortably, Crowley digs into Castiel's vessel through his gunshot wound and painfully digs out the angel tablet from where Castiel has hidden it inside of himself.
As Crowley enjoys his victory, he gets a call from the two Winchester imposters he has tricking Kevin Tran. The two demons inform Crowley that Kevin supposedly gave them the location of his half of the demon tablet, but instead sent them into a devil's trap. Annoyed that the demons are ruining his streak, Crowley leaves Ion to watch Castiel while he goes to deal with the situation, promising to return shortly.
As Ion paces Crowley's office, Castiel questions him on how far he is willing to go, stating that "this charge, it was our mission." Ion questions if Castiel even knows what the mission is and, echoing Samandriel, tells Castiel that "they've been in all our heads." While Castiel feels that the angels aren't machines to be programed and reprogramed, Ion feels that nothing matters. As Ion faces away from him towards the window, Castiel tells him that "you are so wrong brother: it all matters." As Ion is facing away from him, Castiel digs Crowley's bullet out of his wound.
An emotional Ion tells Castiel that "you soldiers, down in the garrison, at least they let you believe the lie. Upstairs, working for Naomi, working in intelligence, we had no option but to live in the dirt. She never reset me completely, I always knew too much. I had to... I had to do my job." As Ion speaks, Castiel comes up behind him and catches the rogue angel's attention. As Ion turns to him, Castiel smashes Ion in the face with a small statue, stunning him. Once Ion is on the ground, Castiel shoves Crowley's angel-killing bullet through his right eye, killing Ion.
With Ion dead and Crowley gone, Castiel is able to escape, heavily wounded.
After escaping, Castiel appears in the road near the Winchesters and asks for their help. Castiel returns with the Winchesters to the Men of Letters bunker where he recovers from his wound though it takes him longer than he expected to heal.
- These events run concurrent to the Second Capture of Kevin Tran. Kevin Tran's actions while captured by Crowley distract Crowley and give Castiel the chance to kill Ion and escape.