"A Series House on Serious Earth" is the pilot episode of Arkham Asylum.
6 months before The Gotham Knight, The Joker and his gang drive their getaway van across a bridge as the police chase after them. Joker orders his men to fire at them which they do, but fail to slow them down, causing Joker to take out his rocket launcher and fires a rocket, which destroys 3 police cars, allowing Joker and his men to escape. Once they make it back to their hideout, Joker's men talk to Joker about splitting the money equally among them. Joker though tells him that he's changed the plan and he takes out a gun and kills all of his henchmen. Suddenly, Joker hears sirens as the Gotham Police swarm the hideout and Joker willingly surrenders as they arrest him. At a courthouse, during his trial, the new DA, Marion Grange, tries to get the judge to give Joker the death sentence due to all of the death and destruction he's caused, but is interrupted by Dr. Hugo Strange, a psychiatrist at Arkham Asylum, who says that Joker isn't to be blamed for his crimes and suggests that he plead for insanity and be sent to the asylum, where he can study and work to figure out the crazy workings of his brain. The judge ends up giving the verdict to have Joker released into Arkham custody to be studied and evaluated to prove if he's insane or not. Later, Dr. Jeremiah Arkham, the head of the asylum, who was in the audience, angrily confronts Hugo for intervening in the trial and for making Joker their responsibility now, due to him believing that Joker is a psychopath that deserves the death penalty, but Hugo reminds him that it's their job as psychiatrists to study the minds of the criminally insane and believes that Joker should be studied and even points out that it's what Jeremiah's father and grandfather, who owned the asylum before him, would've done. Jeremiah then decides to allow Joker to be studied at the asylum, but refuses to let Hugo be his evaluator.
At the asylum, Joker gets led to his new cell, where he meets the warden, Quincy Sharp, along with the corrupt and ruthless head of security, Lyle Bolton. Quincy and Lyle tell Joker how things work in Arkham, but when Joker insults them, Lyle decides to teach him a lesson by beating Joker. He then tosses him in his cell, bloodied and bruised. Quincy then welcomes Joker to Arkham, a Hell on Earth. Meanwhile, Jeremiah meets with their newest psychiatrist, Dr. Harleen Quinzel and tells her about Joker. He then assigns her to evaluate Joker, which Harleen is skeptical about at first, but then agrees, believing it to be a challenge that'll improve her career. The next day, Harleen meets with Joker for their first therapy session. Joker is instantly smitten with her, but Harleen tries to get him to tell her about his thoughts, feelings, or life, but Joker refuses and instead, insists that she tell him about herself. Harleen refuses and instead writes down some notes. Joker though manages to take her clipboard away and reads what she wrote about him, that he suffers from delusions, depression, along with homicidial tendencies. Joker says that the way she puts it, she makes what's wrong with him sound so simple with her labels. He then tells her that he wants to be here since he's got shelter, free food, free drugs, and pleasant company. Unknown to them, Dr. Arkham and Dr. Strange watch the security camera footage of the session. Hugo says that Joker is a complex case and requires a professional and experienced psychiatrist, not someone like Harleen, who's new to the asylum. Jeremiah though turns him down and says that Harleen did well in her first session.
In his office, Warden Sharp admires a portrait of Amadeus Arkham, Jeremiah's uncle and the founder of the asylum, where he finds a hidden message behind the portrait that Amadeus left behind, which says that he saved Gotham and the asylum, but at the cost of his sanity.