Keep Calm and Carry On is the 1st episode of Season 12. It aired on 13 October 2016.
Directly picking up from the previous episode, Dean is shocked to find Mary standing right in front of him, alive and asks if she is real. When he goes to touch her, Mary, having not seen Dean for thirty-three years, doesn’t recognize Dean and tackles him to the ground, asking where she was.Dean assures he's her son, and retells her the story of how she and John Winchester met, to prove it. When Mary finally absorbs that she is alive in the time long after hers, she gives him a hug.
On the other side of the state, a truck driver is driving on an empty road when his radio goes static, and a meteor-like object flies past and then crashes right next to his car. Curious, he looks into the crater to find a man climbing out. It is revealed to be Castiel, who was banished from the Men of Letters bunker from the previous episode. After asking for directions and stealing the man’s car, Castiel drives back to Lebanon, Kansas.
The reunion between Dean and Mary is filled with stories from Mary’s missing time -- how John died and the way Dean and Sam lived since she died, even when Dean met younger Mary,through time traveling with Sam and Castiel. Dean promises to explain more about their life after they’re back home in the bunker.
Lady Toni Bevelli, from the Men of Letters London Chapterhouse takes the
captured Sam him to a veterinarian, Dr. Gregory Marion, to have his bullet wound she gave him, treated before she can interrogate him.Crowley is starting his mission in search for Lucifer. He knows that the archangel is currently jumping from one vessel to another, looking for the right one. As he's found a family whose members have all been used as vessels by Lucifer –- and left them burned out when he moved out –- two demons enter the house to clean up the corpses.
After his wound has been treated, Sam awakens, being held a prisoner in the cellar of a house where Toni and her assistant, Ms. Watt, start the interrogation, accompanied by torture. From Toni, Sam learns that the London Chapterhouse has been watching him and Dean for years, ever since they stopped the first apocalypse. Now they’d like to know about the Winchester boys, other hunters in America, and how the boys managed to save the sun. Sam doesn’t understand and asks if they knew about them all along, why they didn't come for help. Toni replies that they had orders from their superiors that they shouldn’t interfere with the American issues until The Darkness showed and almost killed the sun. Then they agreed that things need to change. Toni tries to convince Sam that they are actually come to help, but Sam doesn’t believe her. Sam laughs at the threat of torture, saying that he has been tortured by the Devil and there’s nothing that Toni can do that will make him surrender.
Dean and Mary arrive at the bunker, where she's surprised to find out that the Men of Letters was actually real, not some old Hunter’s tale. Dean is more surprised to find trails of blood on the bunker’s floor along with an angel banishment sigil on one of the walls. Sam and Cas are nowhere inside the bunker. Dean hands one of the guns from under the war room table to Mary and tells her to stay put. Mary is looking at one of the bookshelves when she hears the bunker door open and footsteps going down the stairs. She confronts the stranger (revealed to be Castiel), only to have Dean stop her. Dean hugs Castiel tightly while being asked about how he’s alive, and Dean also promises him that he will explain after they know where Sam is. Mary asks if Cas is a hunter, and Dean makes the introductions.Cas tells Dean about what happened in the bunker, and he doesn't know what happened to Sam. After hacking local traffic cameras and finding a suspicious car, the three go on their new hunt.
In the barn, Sam is still facing the torture from Toni, who also shares how the British Men of Letters works.Sam continues refusing to answer Toni's questions, and she finally walks away and lets Ms. Watt continue the torture.
Inside the house of Lucifer’s victims, the two demons are still disposing the bodies, when Crowley decides to show up. He points out the vessel-hopping is a sign that Lucifer is weak. He is mocked by the demons, who jeer that he will never beat Lucifer, even in a powered-down state. Crowley stabs the two demons and starts looking for the fourth member of the family, that was shown in a photo, but is nowhere to be seen inside the house.
Back in the barn, Sam survives torture from Ms. Watt that involves a blowtorch, without having to say a word about American hunters. Ms. Watt suggests that Sam is too strong for her to break and asks Toni to call Mr. Ketch, which Toni vehemently refuses to do. Starting to feel a little desperate, Toni decides that they have to start playing with Sam’s mind.
Meanwhile, after Dean, Cas, and Mary find their first lead from the driver of Toni’s car, they make a stop for Dean to do some research. Cas shares his first 'arrival' on Earth to Mary, who in return tells him that she never thought to be the person she used to hear stories about, being brought back to life. Their conversation comes to an end when Cas spots the vehicle that was mentioned by the driver before.
They follow the car to Dr. Marion’s practice and interrogate him about his guests. After the veterinarian mentions that he has Toni’s number, they make a call to let her know that Dean, Cas, and Mary will come to get Sam. In a panic, Toni sends Ms. Watt to meet Dean’s group, while she’s watching over Sam who’s under the influence of her hallucination potion, which makes him see people for whose deaths he feels responsible.
Meanwhile Ms. Watt slams her car into the Impala and attacks Dean and Cas using magic infused-knuckle dusters. She almost brings them down, but Mary stabs her using Castiel’s angel blade. After disposing of Ms. Watt’s vehicle, Dean comforts his mother who is still in shock over killing her and finding herself again a hunter. Dean assures her that he believes that what he and Sam have been doing for years has made the world a better place to live in.
While Dean and his companions continue the search for Sam, the younger Winchester is dealing with the hallucinations, and they grow so intense, he stumbles over to a broken mirror, takes a broken shard, and slits his neck, seemingly killing him. Toni enters the basement and in a panic, checks on him but Sam who had tricked her, attacks her, making his way to an exit. He overpowers her for a moment, but she succeeds in escaping and shutting the door to keep him captive. Sam crumbles in despair as the episode ends.
- Jared Padalecki as Sam Winchester
- Jensen Ackles as Dean Winchester
- Mark Sheppard as Crowley
- Misha Collins as Castiel
Featured Supernatural Beings Edit
- Bad Boys by April Wine (plays over "The Road So Far" recap of events)
- Diesel Smoke, Dangerous Curves by Tom Powder (plays in the radio of the truck as Castiel comes crashing through the billboard
- Solitude by Black Sabbath (plays over the closing montage)
|“||I grew up with hunters, I've heard about people coming back to life before. But to actually do it, after thirty years... A lot's changed. A lot.||”|
|“||I've been tortured by the Devil himself. You... you're just an accent in a pantsuit. What can you do to me?||”|
- The episode was watched by 2.15 million viewers and got a 0.8 rating.
- According to Emma Peterson, a producer on the show, Jensen really did break a phone with his bare hands. 
- This is the fifth episode where Sam and Dean deal with a strictly human antagonist. Other episodes include: The Benders, Family Remains, Thinman and Just My Imagination.
- For the first time Misha's billing in the opening credits reads "and Misha Collins." This type of credit, sometimes called "last billing," is typically contractually negotiated by well-known actors in supporting roles.
- Sam is shown the visions of the deaths of Charlie Bradbury, Kevin Tran, Sarah Blake, Dean, Meg Masters, Mary Winchester and Jessica during his drug-induced mental torture.
- This is the first episode that we see that angels appear as comets crashing to Earth when they are banished.
- The billboard Castiel crashes through is an ad for a Mystery Spot, like the one featured in the episode of the same name.
- "Keep Calm and Carry On" was a slogan on poster produced by the British government for the lead-up to the World War II. The term itself coined by UK's temporary Ministry of Information on 1939 regarding the public safety. After its reemergence in 2000, the phrase later became well-known again, leading the phrase entering the meme world during 2007 and widely spread to the internet during 2009 - 2010.
- Dean's phone conversation with Toni is a reference to Taken when he promises to 'take her apart' if Sam doesn't come back in one piece.
- Castiel landing in a corn field is a reference to the landing of Superman in Kansas, through a billboard near a pickup truck.
- Dean mentions he, Sam, and Castiel all time traveled to meet past Mary, which happened twice, in the episodes, In The Beginning, and The Song Remains the Same.
- He also mentions of Mary seeing the boys as a ghost. This happened in Home, when Mary appears as a ghost to save them from a poltergeist.
- The two demons employed by Lucifer to clean up his mess are Jervis and an unnamed demon. The former previously appeared in "Our Little World" while the latter previously appeared in "We Happy Few".
- Colin Lawrence, who played Dr. Gregory Marion, previously played Jason in Faith, and Reggie Hull in Free To Be You and Me.
- Ronald Patrick Thompson, who played the truck driver, previously played the security guard in The Things We Left Behind.