Dr. Kirk Langstrom, also known as Man-Bat, is a criminal and a patient at Arkham Asylum.
In Gotham City, the yellow rings of Parallax head to Arkham Asylum. There, Batman and Nightwing are doing their best to contain the newly powered inmates of Arkham, including Man-Bat, who have already been transformed into Yellow Lanterns. Luckily, Superman arrives just in time to offer assistance to Batman and Nightwing.
Superman is fighting with Man-Bat and before taking him down, Superman says to Man-Bat that if there is more man than a bat inside of him then he takes no joy in this.
Emil Hamilton succeeds into finding a way to reboot the rings so when he does all the Yellow Lanterns, including Man-Bat, are released from the influence of fear and lose their powers with the rings turning black.
After their rings get rebooted and they lose their powers, the inmates of Arkham fall from the sky unable to do anything to escape from their eventual death but fortunately Superman manages to save them all.
After Parallax's defeat, all the now depowered criminals return to Arkham Asylum.
In the Comics
Dr. Kirk Langstrom, a scientist specializing in the study of bats, develops an extract intended to give humans a bat's sonar sense and tests the formula on himself because he is becoming deaf. The extract works, but it has a horrible side effect: it transforms him into a hideous man-sized bat. The serum also takes away his intelligence, so he goes on a mad rampage until Batman can find a way to reverse the effects.
Later, Langstrom takes the concoction again and Man-Bat returns. He also coaxes his wife, Francine Langstrom, into drinking the serum and she goes through the same transformation, becoming She-Bat. Together, they terrorize Gotham City until Batman can once again restore them.
On some occasions, Langstrom takes the serum and retains enough intelligence to work for the forces of good. During one of these periods he works with the detective Jason Bard.
Kirk and Francine have a daughter Becky and a son Aaron. Because of the effects the serum had on Aaron's DNA, he is born with a deadly illness. Francine turns him into Man-Bat form to save his life.
In Batman #655, Talia al Ghul ties up and gags Francine and then threatens to poison her if Kirk does not give her the Man-Bat formula. After Langstrom gives her the formula, she releases Francine as promised. Talia utilizes the mutagen to turn members of the League of Assassins into Man-Bats.
During Battle for the Cowl storyline, following Batman's death, Kirk is haunted by nightmares of becoming Man-Bat and killing his wife. When Francine disappears, he takes the serum and tries to follow her. After an altercation with the Outsiders, he returns to his human form and is captured by Doctor Phosphorus, who reveals the serum is not necessary to trigger the change. Kirk discovers that Phosphorus has also captured Francine and becomes Man-Bat to save her.
In the New 52, Talia al Ghul had an agent steal the serum from Langstrom's laboratory to use on her soldiers in her plot to destroy Batman. Ignatius Oglivy also comes into possession of the Man-Bat serum which he uses as an airborne virus to spread throughout Gotham City. Kirk Langstrom first appears where he and his wife Francine are escorted by Batwoman to Batman's location. Langstrom reveals that he is the creator of the serum intending to help deaf people. Taking responsibility as the creator of the serum, he uses a sample of the serum Batman had obtained to inject himself. This creates an anti-virus which also spreads through the air. Unfortunately, Langstrom is turned into a Man-Bat (the last remaining Man-Bat) as his anti-virus cures the remaining citizens of Gotham.
After reverting from the Man-Bat form, Langstrom becomes addicted to the Man-Bat serum, taking it every night. However, he apparently does not remember his actions from the night, worrying that a string of reported killings is his fault.
During the Forever Evil storyline, Man-Bat is among the villains that were recruited by the Crime Syndicate of America to join the Secret Society of Super Villains. Scarecrow and Man-Bat attempt to steal the frozen Talons from Blackgate while Penguin is having a meeting with Bane. Bane arrives at Blackgate as Man-Bat and his fellow bats are attempting to transport the Talons to Mr. Freeze and is able to keep one from leaving.