Born Hans Grüper, Arden was a sadistic Nazi doctor of torture and science. In the early 1930s, he attended an underground brothel in Germany, where he observed the acts of Elsa Mars, a dominatrix who performed men's cruel and painful fantasies upon them. In 1932, during the making of a gory snuff film, he and several other masked men amputated her legs with saws from the knee down. Elsa's friend and lover, Massimo Dolcefino, saw it as his goal to murder every man who took part in the act. When Dolcefino got to Grüper, he failed to kill the Nazi and was instead captured and tortured daily by him.
In the 1940s, Hans began running concentration camps, and soon reached the prime of his Nazi position.
In the late 1950s, Hans fled to the United States after Hitler's downfall, changing his identity to "Dr. Arthur Arden" in order to avoid persecution. He became the supervising physician at Briarcliff when it was a tuberculosis ward; when it became an asylum for the criminally insane in the 1960s, Monsignor Timothy Howard allowed him to stay under the belief that his research could aid humanity. Arden regularly performed torturous experiments on the patients of Briarcliff and did not believe in using an anesthetic, as it "interfered with [his] readings". Arden's lab was sealed off from the rest of the asylum's staff, affording him the privacy to pursue his twisted experiments undisturbed.
Arden's life goal was to make a new evolution in human life; one which would usher the human race into a stasis of complete immunity and immortality. However, he only succeeded in creating zombie-like creatures.
Personality and Appearance
Dr. Arden was a man of science with little regard for the archaic, religious practices of his employers. However, he was not without a twisted moral code, as he expressed great disdain for vulgar, loose women. He loved fine wine and Chopin. He had also made anti-Semitic comments on numerous occasions. A small box on his bedroom dresser contained Nazi memorabilia and a series of amateur photos depicting women bound, beaten and perhaps dead, giving credence to accusations of war crimes and suspicion in a police homicide investigation.
He was an older man, standing tall at 6′7″, with a shaved scalp and Van Dyke beard. Arden suffered from microphallus.
Dr. Arthur Arden was the chief physician at Briarcliff Manor, a position he had held since the Manor was a tuberculosis ward. He used his position to whisk away "physically ill" patients with no family members. All were quickly labelled to have died of natural causes and allegedly cremated. He soon came into regular conflict with Sister Jude, who was suspicious of his motives and the circumstances surrounding the missing patients. In actuality, Dr. Arden was conducting horrific experiments on the inmates he kidnapped before tossing them into the forest as severely-mutated "creatures", surviving on regular feedings of raw meat and preventing patients from escaping. He took an interest in Kit Walker, the man accused of being the serial killer "Bloody Face" and claiming to have been abducted by aliens, and decided to experiment on him. While doing so, Arden found a microchip embedded in Kit's neck, which quickly sprouted legs and began jumping around. Though shocked, Arden kept it in a jar in his office, curious of its origin. 
Arden enlisted the aid Sister Mary Eunice to discreetly take large chunks of meat out to the forest at night to feed his "creatures"; inmates who had been altered by Arden's experiments. Dr. Arden had also developed feelings for the young woman, as he found her purity and innocence attractive. Shelley attempted to seduce Arden in exchange for letting her out into some open air, but Arden rebuffed her and expressed cruel disdain for her over her promiscuity. Later, using the alias Stanley, he solicited the services of a prostitute and served her dinner before sending her to his bedroom to don a nun's habit. Anxious about the time she was taking, he forced the door and found that she had discovered his secret stash of Third Reich medals and photos of young women in bondage. He attempted to rape her but was bitten on the arm and kneed to the groin by the woman before she escaped. 
Dr. Arden later experimented on Kit again, attempting to find more technology embedded in his body. He expressed his belief that Kit, while waiting to be transferred to Briarcliff, was recruited by communist agents to help infiltrate his lab. He attempted to torture answers out of Kit but found none. Later that night as a storm approaches Briarcliff, Arden opted to spend the night and was approached by the a possessed Sister Mary Eunice. Though at first cordial, she soon attempted to seduce Arden and talked dirty, which horrified him and caused him to kick her out of his office. He was distraught by this latest development in their relationship. Sister Jude, who was also unknowingly being tormented by the demon possessing Sister Mary Eunice, then confronted Arden in his office over his attempts to seduce the younger nun. The two argued, with Sr. Jude accusing Arden of trying to torment her with her own dark past in an attempt to take over control of Briarcliff.
Unbalanced by the days' events revolving around the two nuns, Arden wandered through Briarcliff during the storm and desecrated the asylum's statue of the Virgin Mary with red lipstick, calling it a "whore" and smashing it to pieces in the lobby. He then caught Shelley in her attempt to escape and forced her into his office with the intent of raping her. When Shelley began laughing at some peculiar condition of his penis, Arden knocked her out, took her to his lab and amputated her legs. 
Following the amputation on Shelley, a new inmate enters Briarcliff claiming to be Anne Frank. Upon her encounter with Dr. Arden, she attacked and claimed that his real name was Hans Gruber, an ex-Nazi scientist. "Anne" was pulled away from Arden and taken to a cell. Arden was then taken into his office and was questioned by two Detectives about his assault on the prostitute. They mention his collection of Nazi memorabilia and pictures of women in bondage. Enraged, Arden became defensive and denied all accusations. Due to lack of evidence, Arden was able to leave the interrogation and returned to his lab. While taking care of Shelley, he received a phone call from Mnsr. Howard stating that Arden's cover story was in danger and that he needed to get his work in order.
"Anne Frank" then burst into the lab, pulled out a gun and quickly shot him in the leg. "Anne" demanded the keys to his secret room after hearing strange and raspy groans coming from behind the door. He refused and was shot again in his other leg. After realizing that he had no choice, Arden threw the keys to "Anne" who then opened the door only to find a blistered and deformed Shelley begging to be killed. Rather than comply with Shelley's wish, "Anne" forced Arden to Sr. Jude's office, only to encounter Sr. Mary Eunice. The nun hurried away to take care of his lab and hide the evidence of Arden's experiments, just as the security guard Frank arrived to subdue and sedate "Anne".
Meanwhile, Sr. Jude had taken "Anne's" claims to a private detective by the name of Sam Goodman, a Jewish European immigrant who has made it his mission to track down unpunished Nazi war criminals for no profit. An investigation on Arden was already underway by the time "Anne" attacked Arden. Sr. Jude further interviewed "Anne" after the latter awoke from her sedation. "Anne" continued to claim that Arden was Hans Gruber, and that he kept a "creature" captive within his lab—despite earlier searches by Jude and Frank proving fruitless. This interview was interrupted by the arrival of "Anne's" husband.
Dr. Arden later returned to his lab to find out from Sister Jude the truth about "Anne Frank" - her real identity was a disturbed, Holocaust-obsessed housewife named Charlotte Brown. He became furious that Sr. Jude allowed her to leave Briarcliff and demanded the Nun beg for forgiveness. Sr. Jude refused and Arden threatened to have Mnsr. Howard terminate her. In a fit of anger, Jude left the office. Arden then undressed and began to tend to his bullet wounds. Sr. Mary Eunice then entered and offered her assistance. She explained that she had removed Shelley from the lab and that once Sister Jude is removed, Arden would need a "strong right hand." With a smile, Arden agreed. Shelley was later found dumped on the grounds at a nearby elementary school by school children and was admitted to a hospital.
Charlotte's husband returned her to Briarcliff, fearing to leave her alone with their son. After Arden visited Charlotte in her cell for unknown reasons, he ran into her husband, who apologized for her shooting him. A resentful Arden then assured that he could 'fix' her and have her home within hours. With the consent of her desperate husband, Arden performed a trans-orbital lobotomy upon Charlotte. With the operation a success, Charlotte seemingly took on the persona of an adoring pliant housewife and doting mother, happier than ever. Though she had begun to pack away her wall of Holocaust photographs and articles, one picture revealed a familiarly sinister face among the officers surrounding Hitler; a young Arthur Arden, A.K.A Hans Gruber.
Arden claimed that his experimental subjects were the next stage in human evolution. He introduced his latest subject, the pedophile Spivey, whom Arden claimed could now survive a nuclear attack. The Monsignor, disgusted, threatened to expose Arden's work, but Arden said that such disclosure will uncover all of Briarcliff's dark secrets, causing Howard to shrink back from his intended exposition.
After Sr. Jude had obtained Dr. Arden's fingerprints from a wineglass with which he toasted her practical defeat in the workplace, Sam Goodman was able to verify that Arden was in fact Hans Gruber. Though Sr. Jude had initially given up on the investigation after the discreditation of "Anne Frank," his confirmation of her suspicions prompted Sr. Jude to visit Goodman's apartment to pick up his file on Gruber. Unfortunately, Sr. Mary Eunice intercepted Goodman's next call, murdering him and threatening Jude into silence. Though she presented Arden with Goodman's file, she hid parts of it as insurance against him betraying her. He raged about having to hide this solitary life, and he questioned her motives in protecting him. She cautioned him to trust her with his soul and that everything will work out.
After finding out about Grace's life-threatening uterine hemorrhage, Sister Mary Eunice rushed into Arden's office and began to berate him and proposed a botched sterilization. Confused, Arden began to deny any involvement in this said surgery. Angry, Dr. Arden then began to scold Mary Eunice for her taking such a tone with him. He demanded respect for his higher authority and then slapped her. Mary Eunice flinched back and threatened: "If you ever touch me again, you will die." Appalled, Arden began to raise his hand once again to strike her when the Devil took over and telekinetically threw Arden across the room. With a grin, Eunice stared down at him and remarked, "I hope this clarifies the chain of command, Arthur."
Not wanting to take the blame for Grace's botched surgery, Arden entered her room, told her of the accusations that were thrown upon him, and treated her in order to set the record straight. Shortly afterwards, Grace is in the kitchen, looking much better, such that one nun calls her "Dr. Arden's little miracle."
Frank talked to Arden, wanting to tell the authorities about Kit and the monster that attacked and killed the nun. Arden relayed this information to Sr. Mary Eunice; she agreed to take care of it. During the Christmas festivities, Arden brought Sr. Mary Eunice a gift, which turned out to be gorgeous drop ruby earrings. Arden told her that the earrings belonged to a Jewish woman in the concentration camp, who always complained of stomach problems. One day he followed her to the bathroom for a stool sample and found her digging through her own feces; to hide the earrings, she swallowed them and reclaimed them cyclically. Sister Mary Eunice happily dons the earrings, disappointing Arden; he expected her to recoil in horror, as the Mary Eunice he used to know would have. Arden visited Jude as she talked to Mother Superior, pleading for her help with Sr. Mary Eunice. Jude agreed to help, but made him swear that he would listen to her. Arden let Jude back into Briarcliff, but betrayed her, remaining loyal to Sr. Mary Eunice. Jude was then trapped in her office with the murderous Leigh Emerson. He later took Grace's dead body down to the death chute, only to be confronted by a high-pitched, alien whine and bright lights, knocking him to the ground. After the disturbance, Arden was confused when he realized that Grace's corpse had vanished.
Arden, Sr. Mary Eunice, and Leigh (who had survived the previous encounter with Sr. Jude) all testified against her and framed her for the murder of Frank McCann, while The Monsignor and Mother Superior testified that Sister Jude was becoming unstable and delusional. Dr. Arden found Kit and took him back to his office, where Arden verified Kit's alien story as he himself had suffered a brief encounter. Arden also noticed that the extraterrestrial visitors seemed to appear each time Kit impregnated a woman. Arden believed that the extraterrestrials were using Kit as a subject in a eugenics experiment, and that bringing him to the brink of death would draw them out. Kit goes along with Arden's plan, for the chance to be reunited with Alma. Arden injects potassium chloride into Kit's heart muscle, causing him to convulse and eventually stop breathing. Arden's predictions proved true as the aliens appear shortly after Kit stops moving. After an array of bright lights and noises, Arden walked into a normally empty room to find a communicative Pepper; along with a nude and fully pregnant Grace, who verified her pregnancy by placing Arden's hand on her stomach.
Arden resuscitated Kit and hid the truth from him, claiming that there was no visitation from the extraterrestrials. He examined Grace, who had miraculously healed from her bullet wound and seemingly become 9 months pregnant in a few short weeks. He interrogated Pepper, who had been aiding in Grace's protection on the extraterrestrials' behalf. Pepper claims that Grace is protected from any harm Arden might intend towards her; and furthermore, that the extraterrestrials see Arden, along with his scientific efforts, as a joke.
After planting a cucumber in the room of Judy Martin (formerly Sr. Jude), Sr. Mary Eunice recommended electroshock therapy; Arden concurred, covering it up as a treatment for Judy's "clear-cut" signs of manic depression. Despite his warning to restrict the electric current to 50%, the sadistic Sr. Mary Eunice turned it nearly all the way to 100%.
Arden eventually walked in on and witnessed Sr. Mary Eunice forcibly strip Monsignor Timothy Howard of his virginity while discarding her own. He was disturbed by this final shedding of Mary Eunice's virtue.
Arden's afternoon feeding of the Raspers/Creatures is interrupted by Sr. Mary Eunice. He was greatly repulsed by her actions. Sister Mary Eunice wanted Arden to lobotomize Judy but he refused, unwilling to be her pawn any longer. Arden executed each of the Raspers/Creatures with a Luger P08 pistol, claiming the experiment had come to an end. He approached suicide by nearly shooting himself in the head, but faltered, despairing at finally having "lost" Mary Eunice forever. The unmoved Sr. Mary Eunice called him pitiful. In response, he begged her to take pity on him, though it is unclear whether he wanted her to show him affection or kill him. Instead, she shoved him aside and walked away.
After Sr. Mary Eunice's death, Monsignor Timothy Howard proposed a traditional Christian burial, but Arden insisted that the best option would be to cremate her - largely due to her possession but perhaps also in order to cover up evidence of her crimes. He further volunteered to perform the cremation himself in solitude.
While in the crematory, Arden stroked Sister Mary Eunice's hair wistfully. With her gone, the extraterrestrials scornful of his achievements, his nemesis Sr. Jude reduced to imbecility and his 'Raspers' experiment a failure, he had nothing left to live for. Sobbing, he laid on top of Sr. Mary Eunice's corpse and flipped the switch, choosing to be burned alive with the girl he once loved.
Others would later make note of Arden's mysterious disappearance. Oliver Thredson had considered pinning the Bloody Face crimes on him as part of his bargaining with Kit, though he was found out before he could pursue this. Some time during the 1970s, when Lana interviewed Timothy Howard (now Cardinal of New York) on his involvement with Arden, the doctor was still believed to have disappeared rather than being presumed dead.
- Arden is the third character to make a crossover appearance in another season.
- Arthur Arden has been absent in two episodes overall throughout the Asylum season. Those episodes are Spilt Milk and Continuum. In both of them, the cause was his confirmed death by cremation in The Name Game. In Madness Ends, he only appears briefly in archive footage.
- Dr. Arden's character could be based upon the real life Auschwitz doctor Josef Mengele, who performed "unnecessary surgical procedures" on twins, girls, children, and other prisoners of war, including amputation, chemical injections and brain surgery, all without anesthetics. He was described by ex-prisoners and SS officers as "deceptively friendly and kind" to those who he enlisted for his experiments, and earned a nickname for himself as the "Angel of Death". In "I Am Anne Frank: Part 1", Hans Grüber, during the flashback, is seen as falsely friendly and kind, offering the prisoners chocolate. He however specifically targeted young children and twins for his experiments, all of which mirror the actions of Mengele.
- Arden's interest in the extraterrestrials coincides with the fact that James Cromwell, who portrayed him, previously played the role of Zefram Cochrane in Star Trek: First Contact. In the "Star Trek" universe, Cochrane was the scientist who initiated the titular first contact between humanity and alien life.
- Ironically, the fate of Arden - the former Nazi scientist - mirrored that of many of the victims of the Auschwitz death camp in which he once worked: burning in an oven. This was an intentional ironic punishment by the series' creators, as explained by Ryan Murphy: "I also think the image of a Nazi doctor going into an oven is sort of a brilliant metaphor of him literally paying... I thought his end was very justified and somewhat poetic." 
- The younger Hans Grüber seen in flashback in I Am Anne Frank: Part 1 and photographs in Part 1 and Part 2 is played by James Cromwell's physically similar son, John Cromwell.
- James Cromwell, a veteran actor of comedies and historical dramas, was initially unprepared for the darker tone represented by his character, and indeed the show. When interviewed, he admitted that “I got the first four scripts, and my first reaction was ‘What have I gotten myself into!?’”. Discussing his performance, Cromwell implied that Arden's character traits were entirely a product of script and performance, and not drawn from any personal anger or disturbed thoughts. 
- Dr. Arden carries the same cane that belonged to the vampire Barnabas Collins on Dark Shadows. Ryan Murphy has admitted to being a fan of the series, which also had a repertory cast that would play different roles in different eras and story arcs. 
- Arthur's last name, Arden, means "[they] burn" in Spanish. Arthur Arden dies being burned in a crematory oven.
- To Sister Jude: "I'm not one of your charges, Sister, quaking in my boots."
- To Sister Mary Eunice: "Oh, Sister, life is too short for regrets!"
- To A Prostitute: "Show me your mossy bank."
- To A Statue Of The Virgin Mary: "Whore!"
- To Kit: "Quiet, son. You don't belong in here; not when there's so much to learn."
- To Kit: "I hope you don't mind, if I don't use anesthetic. It interferes with my readings."
- To Kit: "The devil doesn't reside in hell, Mr. Walker. He lives right here in the frontal gyrus; the optical lobes. Inside those beautiful brains lies the secret of understanding the darkness of the human psyche, and ten of them put together are not as dark as what resides right here in this cute, blond melon."
- To Sr. Jude: "A ferret...delightful creature. I used to keep one as a pet...until it bit me and I broke its neck."
- To Kit: "You can swear all you like, Mr. Walker, but I will get to the truth. In here...we have all the time in the world."
- To Shelley: "Am I supposed to be moved by that pathetic tale of woe?"
- To Shelley: "You were a very naughty girl last night. You tried to fly away, so I had to clip your wings."
- To Anne: "You wanna know what goes on in here? You're about to find out!"
- To Kit: "Through which orifice?"
- To Kit: "No, Mr. Walker. I want to almost kill you."
- To Kit Walker: "Hello, Mr. Walker. I'm Dr. Arthur Arden. I run this institution."
- To Shelley: "Get your filthy hands off me!"
- ↑ 1.0 1.1 Episode: The Name Game
- ↑ 2.0 2.1 Episode: Tricks and Treats
- ↑ Episode: Welcome to Briarcliff
- ↑ Episode: Nor'easter
- ↑ Insidetv.EW.com, American Horror Story, Ryan Murphy - the Name Game Exclusive
- ↑ ‘American Horror Story: Asylum’ Star James Cromwell Talks Heath Ledger, Distancing Himself From Dark Dr. Arden
- ↑ Collinsport Historical Society.com, Ryan Murphy talks "Dark Shadows"