Batman: Harley Quinn is the live action movie based on a comic with a same name.
The Movie begins where an local girl named Jenny was walking home from work at night on christmas holiday, she was an beautiful lawyer who has an abusive boyfriend named Maximilian Wilson. He develops a dangerous obsession with her and starts threatening her. Batman discovers Jenny's been blackmailed by her boyfriend and manage to help her. A few nights later,Jenny tries to contact Batman, but he is ambushed by Max and his friends, threatening to beat Jenny. When she arrives and he makes her lose control and arrest him. Thanking Batman, Jenny decided to leave Gotham after Christmas.
Six months later, Poison Ivy was delivering the harvest from Robinson Park's trees to Gotham City but on her way she found a wrecked rocket and she started to clean the way. After a while Ivy heard a voice coming from the inside of the rubble. When Ivy cleared enough debris, a woman dressed as a clown came out of it and fainted before she could explain what happened. Ivy considered it for a while and then she took the girl to her hideout inside the park.
When the girl regained consciousness, she discovered that Ivy has tended her wounds, taken off her costume and was looking after her. Posion Ivy told her that she recognized her from Arkham Asylum and the girl told Ivy that her name was Harleen Quinzel and that she used to work at Arkham Asylum before the earthquake. Quinzel explained Ivy how she ended up in a rocket that crashed in Robinson Park. During her first days as an Arkham orderlie, Quinzel became attracted to the Joker and both began a furtive relation inside Arkham. Quinzel helped the Joker on his may escapes from the Asylum and she was eventually discovered. Jeremiah Arkham was upset at Quinzel and he decided to lock her in solitary confinement in the asylum's basement. She didn't mind because she knew that Joker would come back to rescue her. As days passed she was starting to lose hope but suddenly, the doors of her cell opened up. Quinzel stepped out of the cell and found that the Asylum was heavily damaged as a result of the earthquake. She took up one of the asylum's vans and used it to reach Gotham until the van ran out of fuel. She was roaming the wrecked streets when she spotted some police officers trying to save some people's lifes. The officers asked for her help but she was overwhelmed by the look if the victims. They were all smiling with the grim rictus caused by Joker Venom. As the victims were not dead, Quinzel asked one of them where did it happened and they told her that it was in a store nearby. Quinzel ran away without helping the officers and entered into a costume shop. She tried some costumes in order to join the Joker and in the end she decided to stick with the black and red jester costume and also she started calling herself Harley Quinn. She started looking for Joker and she knew that he would be where people went to get weapons.
The Joker and his henchmen were at the improvised Iceberg Lounge, asking Penguin for some ammunitions and weapons. Penguin refused to give them weapons and when things were about to became messy, Harley arrived at the scene and attacked Penguin and his henchmen. The distraction was used by the Joker who killed the Penguin's henchmen and forced him to surrender his weapons. Joker recognized Harley from Arkham and they got out of the place with Penguin's weapons.
After some time being on the road, Harley found a cave near an abandoned amusement park and decided to decorate it for it to be their new hideout. She worked really hard and transformed a lifeless cave into the perfect hideout for her and the Joker.
Harley then told Ivy how wonderful were the days with Joker and how Joker managed to seize control of all the areas surrounding the amusement park. The Joker's activities attracted Batman to his territory and Joker commanded Harley to go and deal with Batman. She was happy to help and when she faced the dark knight, she managed to attack him by surprise. In the end, Batman won the fight and before leaving Harley used a couple of bombs to distract Batman and make her escape. Joker and his henchmen were already leaving the place without Harley but she managed to get to their car first and then all of them went to the secret cave. Harley told Ivy that after what happened with Batman, that night she and Joker spent the night together and because she was overwhelmed with joy, Harley couldn't remember precisely what happened but it was one of the happiest moments of her life. Ivy realized that Joker might have drugged Harley without her realizing the truth. Harley told her that the next morning, Joker was nowhere nearby bu that he left a message next to Harley. The message told Harley to meet him at the amusement park old rocket ride. Harley steeped inside the rocket and the door closed behind her. In a screen, Joker told Harley that he couldn't stand feeling the same as Harley and that he was disposing of her by launching the rocket she was in. As the rocket was lifting from the ground, Harley destroyed the control panel out of rage and discovered that if she moved the cables she could actually direct the rocket. Harley tried to land on the Robinson Park's trees but instead she fell to the pavement outside it and that's when Ivy found her.
After telling her story, Harley was really upset and Ivy gave her a drink that make Harley feel sick. The drink was a potion to immunize Harley from Ivy's poisonous touch. The drink enhanced Harley's strength and agility and also make her completely invulnerable to toxins. Ivy repaired Harley's costume and then Ivy asked of Harley to exact revenge against Batman and Joker.
Harley used a make-shift Bat-Signal to attract Batman's attention. Batman arrived and she told him about a plan Joker had that would kill many people. Batman gave Harley a tracking device and told her to go to the place and that he would follow her. Harley tried to make her move on Batman but the man was already gone.
At the Joker's hideout, the clown prince of crime killed one of his henchmen because the man spoke too much information. Harley arrived at the place and tossed the tracking device to the Joker's henchmen. Batman arrived and knocked all of the henchmen down. While Batman was busy, Harley attacked Joker for trying to murder her. Joker was unable to land a punch on her and he decided to use his joker gas on Harley, but it had no effect on her because of Ivy's drink. When Harley was about to deliver the final blow, she was stopped by Batman but with her new strength she managed to stand and fight him. Joker seized the chance to escape but Batman caught him a few moments later. They struggled for a while but then out of nowhere, Harley attacked Batman with a giant mallet. Batman was completely knocked out and Harley went right after Joker. The clown tried to escape using an old elevator from the amusing park but Harley managed to get inside and kicked Joker out of the elevator. Joker was hanging from a shaft and Harley was ready to knock him off to his certain death when the Joker said that he was sorry. Those words were enough for Harley, who helped Joker up and they reconciled.
Batman woke up after being down for what seemed like hours. He walked out to the shore and found Joker and Ivy in a boat on her way to freedom. Harley told Batman something about a note attached to the shore. Batman read it and in the end he realized that the Joker's plan to kill many people was a ruse to lure him in, but that they decided to use it anyway but this time they planned to kill just one man: Batman. Batman jumped to the water and just then the whole amusement park was destroyed in a big explosion.
Later, in the Batcave below Arkham Asylum, Alfred tended Bruce's wounds and after resting a little bit, Batman decided to go back to Gotham to help as much as he could. He knew that he couldn't rest until Gotham was a safe place for the good people and not a haven for criminals and madmen.