Plot
Mad Love begins with Joker, accompanied by his new sidekick, Harley Quinn, and his scheme of killing Commissioner Gordon, which is foiled by Batman. The Joker retreats with Harley, while Batman returns to the Batcave. With his butler, Alfred Pennyworth, Batman discusses Harley's questionable past: while studying in Gotham State University with a gymnastics scholarship, Harley, formerly named Harleen Quinzel, aimed to get a degree in psychology by sleeping with her professors, and planned to become a pop psychologist writing self-help books.
Meanwhile, in his hideout, a frustrated Joker struggles to devise a plan, with Harley attempting to comfort him, which annoys the Joker, inciting him to try to kill her, and later, to kick her out. A bemoaning Harley reflects on her current status as a wanted criminal in love with a psychopath who neglects her, concluding that Batman is to blame for their broken relationship. Harley then recalls her past in Arkham as an intern psychologist looking to profit off of its criminal patients by writing tell-all books, starting with her first encounter with the Joker. Having chosen him as an adequate subject to write about, with Joker luring her by suggesting he would tell her his secrets, Harleen set up sessions with the Joker, in which the Joker seduced an unwitting Harleen by placing himself as sympathetic, telling her he was abused as a child by his father, who was only happy once during a visit to the circus, then implying Batman as another figure who hurt him. As time passed, Harleen concluded that the Joker is a misunderstood figure constantly victimized by Batman, and that she had fallen in love with her patient, which she realizes is partly because he "could make [her] laugh again"[3] when she had long felt restricted from "all amusement and fun".[4] Later, during a week the Joker escaped from Arkham, a worried Harleen is distraught to see Batman returning a heavily injured Joker, inciting her to break him out; in the process, Harleen stole a jester costume and gag items, which she weaponized, from a costume shop, and adopted the persona Harley Quinn, a reworking of her name as a play on the theatrical clown character Harlequin which the Joker had suggested to her.
Harley determines that the only way she can make the Joker love her back is to kill Batman, which she decides to do using the Joker's unused plan of killing him in a tank of smiling piranhas, which Joker abandoned because piranhas cannot smile, a problem Harley solves by hanging the Batman upside down so the piranhas appear to be smiling from his perspective. Harley successfully captures Batman, but he distracts her by telling her truth; the Joker never loved anything or anyone except himself and he had been using her from the start, with the Joker's stories to her of being abused as a child all just lies he has told to others, with the details changing each time the Joker retold them. When she, in denial, tearfully insists the Joker really loves her, Batman convinces her to call him so he will know she would have accomplished her goal, as the piranhas would have left no convincing evidence. The Joker arrives, infuriated by how Harley would rob him of the privilege of killing Batman. Harley explains how using the Joker's plan means he will get credit, but her having to explain that fact at all makes it an unacceptable flaw to him, and he ultimately pushes her out a window, where she falls to the ground and is found gravely injured by nearby police officers. The Joker then decides to use the opportunity to finally kill Batman, which escalates into a chase ending atop a moving subway train. Batman taunts the Joker by saying that Harley, with her plan, had come closer to killing him than he ever did. The Joker attacks him in a fit of rage, and Batman retaliates, ending with Joker falling down into a burning smokestack.
In Arkham Asylum, Harleen denounces the Joker, determined to heal and move on. Lying on her bed a moment later, however, Harleen finds flowers sent by the Joker with a "get well soon" card and falls in love with him again.
