Arthur Ketch is first mentioned while Lady Toni Bevell is torturing Sam for information. When all their methods prove fruitless, Ms. Watt suggests bringing in Ketch; however, Toni is very much against it.
He is also shown in a flashback killing a vampire, identifiable by the tattoo on his hand.
Later on, Mick Davies retrieves Toni and informs her that he has sent for Mr. Ketch, who is shown preparing to leave the UK. This leaves Toni visibly uncomfortable.
In American Nightmare, Mr. Ketch drives up to the Impala on a motorcycle (first seen in the previous episode) and stares at it for a moment before driving away. He later tracks down and kills Magda Peterson, telling someone on the phone that he cleaned up the Winchesters mess and they were correct about the Winchesters being unable to kill Magda.
In LOTUS, Arthur rescues the Winchesters and Castiel from the Secret Service and orders Castiel to wipe their memory before introducing himself. That night, Arthur explains that his job is to "strongly encourage" the Winchesters to work with the British Men of Letters and he was sent by Mick Davies after Sam called him and hung up. Arthur has Castiel confirm that he's not lying and shows them his arsenal of weapons, including a hyperbolic pulse generator capable of exorcising a demon from its vessel. Recognizing its potential, Sam asks to borrow it and for Arthur to trust them. Arthur eventually gives the Winchesters the generator, enabling them to force Lucifer from Jefferson Rooney and send him back to Lucifer's Cage.
Six weeks later, Castiel contacts Arthur and Mick to help him and Mary find Sam and Dean who have been taken prisoner by the Secret Service. The two men are impressed to learn that the brothers had in fact borrowed Arthur's gadget in order to deal with Lucifer himself. They agree to help in hopes that it will earn them the trust of the American hunters, and through their connections, Arthur and Mick locate Sam and Dean near Site 94.
Once the four encounter Sam and Dean, Arthur is unimpressed to learn that they left survivors. Sam insists the people pursuing them were just soldiers doing their job, though Arthur considers it "unprofessional". Sam, Dean, and Castiel head to Mary's car while glaring at Arthur suspiciously. Arthur and Mick watch them drive off and share a knowing look at each other. It is later revealed that Arthur went back and killed all those involved in Sam and Dean's imprisonment, including Agent Rick, Agent Camp, the soldiers and the coroner. Mick reports this while noting that cleaning up loose ends is Arthur's job.
In Stuck in the Middle (With You), Mary visits Arthur after stealing the Colt and tells him the story of its theft from Ramiel. Mary is enraged that Arthur sent her after a Prince of Hell which got Wally killed and threatens to destroy the British Men of Letters if something happens to her sons. Arthur apologizes, claiming not to have known that she was going after a Prince of Hell. Arthur and Mary discuss the legend of the Colt as an excited Arthur unwraps it.
In Family Feud, Arthur accompanies Mary Winchester on a rugaru hunt. Arthur tells Mary he is thoroughly impressed with Mary's hunting skills after she kills three rugarus by herself. Arthur later takes Mary to her hotel and tells her she is one of the best hunters he has ever seen. Arthur also says she is an excellent liar. Arthur tells Mary she should forget her sons as they are a weakness to her.
In The Raid, Mary and Arthur take out a vampire nest together and Arthur expresses his dislike for them trying to recruit the Winchester brothers when they have Mary. Arthur later visits Dean at the Men of Letters bunker and sits down for a drink with him. Rather than trying the sales pitch like the other British Men of Letters, Arthur is frank with Dean about his motives, telling Dean that he is a killer and the British Men of Letters offer him the best chance to express his talents. Arthur sees Dean as the same as him and the two decide to take down a vampire nest together. At the nest, Arthur initially arms himself with a gun but decides to use a machete instead like Dean. The two men find only one vampire hiding in the nest and Arthur beats upon her before Dean stops him to try things his way. When Dean promises to grant the vampire a quick end, she tells them that her nest is going after the British Men of Letters.
Alarmed, Dean and Arthur rush back to the British Men of Letters compound to find that Sam has killed the Alpha Vampire and the surviving vampires have fled. Mick berates Arthur who tells him he was trying to recruit Dean and would've succeeded if Mick's operation hadn't screwed things up. He then punishes the rogue hunter Pierce Moncrieff who they were previously working with.
Arthur offers Mary a toast.
In The British Invasion, Arthur sleeps with Mary following a successful hunt. Mary seems tempted to bond with him further but Arthur seemingly disapproves though he appears intrigued by Mary's attempt to have "the best of both worlds." Arthur is later called back to the British Men of Letters headquarters by Doctor Hess. The two wait for Mick to arrive. Mick shows disobedience and Arthur is ordered to kill his former friend. While the two stare down at Mick's body, Arthur appearing to have some remorse or regret for his actions, Hess announces that every single one of the American hunters must be eliminated.
In The Memory Remains, Arthur sends a text to Sam pretending to be Mick, checking in if the brothers are home. Sam replies they are not, allowing Arthur to enter the Bunker with a few subordinates so they can wiretap it and search for The Colt. While scanning Dean's room, Mick comes across a photo of Mary with a 4-years-old Dean. Once the operation is complete, Arthur returns to his own headquarters, taking the photo with him. By the time Sam and Dean return home, Arthur calls to inform them that Mick has been sent back to London so they must report directly to him, even if they don't like it. After the call, Arthur listens to the brothers' conversation through the wiretap he set up and hears Dean insult his motorbike. Arthur stares at the photo he stole while listening.
In Twigs & Twine & Tasha Banes, Mary discovers Mick's body as well as the fact that the Brits are now targeting American hunters. She angrily confronts Arthur about this. Arthur initially tries to brush Mick's death off as "an unfortunate werewolf mishap", but Mary doesn't believe it, knowing werewolves don't shoot people. The two get into an argument, with Arthur claiming that his murdering of the US Secret Service agents and Magda Peterson as cleaning up after Mary's sloppy sons. Mary disagrees, and the two get into a fight. When Mary tries to make a run for it, Arthur knocks her out using a taser. He then ties her up to a chair and arranges for Toni Bevell to interrogate the hunter since Mary is still too precious of an asset to kill.
Arthur visits Mary while she is being brainwashed by Toni into being a killer for the British Men of Letters. Mary tries to kill herself with Arthur's gun and begs Arthur to kill her as losing her will is the worst thing Mary can imagine. Apparently sympathetic and unwilling to kill Mary, Arthur assures her that it will all be over soon. He also introduces his hellhound to Toni who is disturbed.
Later, Arthur and three of his men ambush the Winchesters in the bunker, ending with Arthur's men killed and Arthur held at gunpoint by Dean. However, a fully-brainwashed Mary enters and forces her sons to release Arthur. Taking Dean's gun, Arthur forces the Winchesters and Toni, who he sees as expendable, to remain in the bunker as he and Mary leave. Arthur reveals that he is initiating a lockdown that will trap the three in the bunker with no power and water and the air being sucked out, resulting in their deaths within two to three days. He later tells an emotionless Mary that it will get easier killing people she doesn't remember loving.
In Who We Are, Arthur sends Mary names of hunters to kill and prepares for a massive operation to wipe out all of the American hunters and their families. After being unable to reach Mary, Arthur has Paige discreetly track her and discovers that Mary is in Lebanon, Kansas. Realizing what this means, Arthur leaves before hunters led by Sam storm the British Men of Letters compound and kill everyone inside.
A bloodied and defeated Arthur Ketch.
Moments after reaching Mary's mind, Dean awakens to find Arthur in the bunker, having murdered Toni. Dean and Arthur engage in a brutal hand-to-hand fight through the bunker's main room that ends with Arthur holding Dean at gunpoint. Before Arthur can kill Dean, he's shot in the arm by Mary whose mind has returned thanks to Dean and Toni. Arthur tells the Winchesters he knew both of them were killers before Mary executes Arthur with a shot to the head. His body is later covered with a sheet by Mary and Dean. It's later revealed that the Winchesters dumped Arthur's body into the waste canal.
Season 13
In War of the Worlds, the Winchesters investigate a series of witch murders and are shocked to discover what appears to be a bearded Arthur Ketch following one of the victims. The Winchesters manage to capture the man who claims to be Arthur's twin brother Alexander, though Dean remains dubious of his story. "Alexander" tells the Winchesters that Arthur wasn't naturally amoral, was "loyal to a fault" and most likely regretted some of the things he did to them. "Alexander", who was hunting Rowena MacLeod, claims to be working as a mercenary hunter and is hunting for Rowena simply because she is a witch. After getting a weird call from Castiel, the Winchesters leave "Alexander" behind in the bunker.
During a fight with a group of demons, "Alexander" suddenly appears to help, saving the Winchesters lives. Following the fight, Dean realizes that Arthur and Alexander are truly one and the same as he'd suspected as Dean recognized Arthur's fighting style along with other inconsistences. Arthur finally admits that Dean is right though he had mostly told them the truth about himself. Arthur is now separated from the British Men of Letters under his new alias of Alexander with his former employers wanting him dead for it if they knew. He is also working as a mercenary hunter. Arthur explains that long ago, he made a deal with Rowena where she supplied him with a Resurrection Seal in exchange for his help in escaping the British Men of Letters custody. After they had dumped his body, Arthur was resurrected. Not willing to trust Arthur, Dean attempts to kill him, wounding Arthur in the shoulder before he drops a smoke bomb and escapes on his motorcycle.
Later, now clean-shaven, wearing a sling on his right arm and dressed in his old suit, Arthur agrees to work for the Prince of HellAsmodeus.
Skills and Abilties
He is a professional killer. He has murdered any 'leftovers' from the Winchester's work without any difficulty. He even cleans up all evidence of these killings or supernatural events. He is also a very capable torturer. He is quite confident about his abilities, as when he and Dean went after a Vampire nest, he choose to use a machete, instead of the Vampire Irradiation Gun because he considered it far less challenging. Arthur is also an expert hand-to-hand combatant, as he was able to overpower Dean for a while, though Dean was injured and disorientated at the time. He apparently has a unique enough fighting style that Dean was able to see through his disguise as "Alexander" just from seeing him fight some demons based on Dean's own fight with Arthur.
Equipment
As a member of the British Men of Letters, he has access to its vast weaponry. The engineers of the British Men of Letters have spent years blending sorcery and technology to produce an advanced arsenal to combat supernatural threats.
Vampire Irradiation Device.
Vampire Irradiation Gun: The British Men of Letters don't always have to cut off the heads of vampires to eliminate them as they have developed a tool that uses radiation to reorder the DNA of a vampire which turns the vampire's own blood into poison that is lethal to them. It is said to be very effective on large vampire nests.
Hyperbolic pulse generator: A device capable to targeting specific angels or demons and exorcising them safely without harming the host. It is capable of removing even an archangel.
Personality
Arthur presents himself as a gentleman of sorts with a strong British accent. He has no qualms about killing people and considers it his job to clean up loose ends. He believes stalking the Winchesters and killing all those they choose to spare as being "professional". He can be a bit of a show off as seen during his formal introduction to Sam and Dean, when he blew up a vehicle belonging to the Secret Service and proudly presented the Winchesters with his vast weaponry. His well-dressed appearance and charming manners clearly hide a much more sinister personality, which Sam, Dean and Castiel begin to notice over time. In a frank conversation with Dean, Arthur calls himself a killer and admits that when he doesn't kill, it bothers him and he works for the British Men of Letters due to their ability to supply him with targets. Arthur sees himself as similar to Dean in this regard and seems to regard Dean as something of a kindred spirit.
Despite his ruthless personality, Arthur does appear to care somewhat about others. After sleeping with Mary Winchester, Arthur brushed off the idea of them having a relationship, but did so in a way that indicated he had in fact wanted one with her. He also appeared somewhat intrigued by the idea of her having "the best of both worlds" by having both her family and hunting. While Arthur murdered Mick Davies on Doctor Hess' order, the expression on his face afterwards suggests that he had some remorse or regret for having done so. When talking to Mary, he tells her that she doesn't know him and she doesn't want to in a way that suggests perhaps he possesses some regret or self-hatred for the things he's done. This is further implied by his words to the Winchesters as "Alexander."
However, Arthur remains a cold-hearted, psychotic individual who believes the ends justify the means. He becomes disappointed in Mary when he realizes she is not as cold-hearted as he had hoped. He considers having a conscience as a trite idea, and considers Sam and Dean as "sloppy hunters" for sparing the Secret Service agents and Magda Peterson. He believes psychics and non-human entities are monsters that deserve torture and death and nothing more.
Despite his cold-heartedness, Arthur does appear to have some genuine feelings and care for Mary Winchester. Starting as admiration, Arthur shows obvious upset that their relationship isn't more after they have a one-night stand. While ordered to kill the American hunters, Arthur did his best to protect Mary in his own twisted way though he didn't hesitate to taser her from behind. Despite this, he appeared to be genuinely distressed by her predicament of being brainwashed and went as far as to attempt to comfort her. Arthur also didn't seem to be able to bring himself to kill her, even at Mary's request despite his ruthless and cold-heartedness. He also appears disquieted by her heartlessness after she is successfully brainwashed. As "Alexander", Arthur makes it a point to ask after Mary and the look in his eyes when Dean responds is a major part of what convinces Dean that "Alexander" is in fact Arthur.
Arthur possesses a great deal of arrogance due to his skills. When Dean tells Arthur he is going to kill him, Arthur tells Dean that Dean won't but Arthur will greatly enjoy Dean trying. He also took great pleasure in taunting Dean through their fight.
While posing as Alexander Ketch, Arthur stated that he wasn't naturally amoral, indicating it was something that he had become. Arthur also stated that he is "loyal to a fault" and indicated that he regretted some of the things he did to the Winchesters. Indeed, after his deception was exposed, he claimed to have simply been a solider on the opposite side of a war rather than someone who had a personal stake in what was being done to the Winchesters. He also claimed to have mostly told them the truth about himself when in their captivity with the indication being that he was only lying about his identity and his return.
Following his resurrection, Arthur adapted a more mercenary mindset, continuing his work but only for those who paid him for it generally. This was seen as he made a deal with Asmodeus to find Jack for impending invasion of Michael.
Physical Appearance
Arthur is a dark-haired Caucasian man who generally wears clean suits. He has a tiny cross on the back of his right hand. After his resurrection, Arthur ditched his suits and wore more casual clothes. He also grew a beard. Following the exposure of his resurrection, Arthur shaved off his beard and resumed wearing one of his old suits. For his disguise as Alexander Ketch, Arthur had his defining cross tattoo removed.
As Arthur prepared to kill Dean, he was shot in the arm by Mary, defeating him. After Arthur told the Winchesters he knew they were killers, Mary executed Arthur with a shot to the head. He was later resurrected by his own Resurrection Seal.
Arthur appears as the killer of avampire in Keep Calm and Carry On when Lady Toni Bevell describes the British Men of Letters activities. He can be identified through both the cross on his hand and the fact that close observation of the blurry killer shows that its clearly Arthur Ketch.
While Ms. Watt implies he's a very proficient torturer, Toni describes him as a psychopath. In return, Arthur calls her "a neurotic, overreaching time bomb" and admits to being her ex-boyfriend and the one person who saw her actions coming. As Arthur is Toni's ex-boyfriend, their dim opinion of each other may come from their former relationship. Indeed, while Arthur is shown to be a remorseless killer in general, after killing Mick Davies he appeared to show regret for his actions, indicating he is not totally unfeeling and uncaring. After torturing a shapeshifter, Mary notes that Arthur did indeed enjoy it. While posing as Alexander Ketch, Arthur himself indicated that he does indeed possess regrets for at least some of his actions regarding the Winchesters.
His name is possibly a reference to the famous executioner Jack Ketch, who made a name for himself as the somewhat barbaric executioner of political offenders in the late 1600s.
Arthur describes himself as an artist who paints in many colors.
According to a shapeshifter, Arthur's eye twitches when he lies. Arthur's response is that his eye twitches all the time, indicating that he is constantly lying.
Arthur indicates that he himself has been tortured as he tells Mary in Twigs & Twine & Tasha Banes that "anyone tells you torture is never the answer, they haven't been under the knife."
Unusually of Supernatural characters, characters - including Sam and Dean - always refer to Arthur by his last name, with Crowley being the only other character thus far to use his first name.
