Challenge of the Man-Bat
In the perfect darkness, a group used night-vision lenses in attempt to break into a gem vault. Batman heard one of them drop a piece of equipment and went after them. They escaped, but he was able to grab their ultrasonic cutting tool. The group planned on luring Batman to their next heist.
Dr. Kirk Langstrom experimented with bats in hopes that he could use their genetic make up to give himself sonar. It worked - he was able to navigate in total darkness. Langstrom grabbed some earplugs so he could drown out the now super intensified "normal" sounds.
Batman and Alfred tested some new hearing aids Batman could use in tracking the "blackout" gang.
Langstrom, on his way home, realized he was growing body hair and claws like a bat. His entire body was mutating.
That night, the blackout gang attacked the museum. Batman was there, but thwarted when they threw ping pong balls out, causing him not to be able to "see" them with his improved hearing. The Man-Bat saw what was going on and helped Batman take down the crooks. Afterwards, he told Batman his was no costume.

Man or Bat?
Man-Bat waited as some men attempted to break into a safe - there was something inside he needed. As soon as they were in, Batman arrived. The two bats took down the criminals, but Man-Bat turned on his hero when Batman stood in his way of getting what he needed. During the scuffle, Batman realized Man-Bat wasn't wearing a disguise.
After regaining consciousness, Batman headed to the museum where he'd first encountered the creature. There, he found Francine Lee, Kirk Langstrom's fiancé, attempting to gain entrance to his lab. The security guard would not let her in. Batman burst in to find the Man-Bat. Langstrom was startled and dropped the chemical he'd taken. After seeing Francine and Batman, he escaped through the window. Batman gave chase, but lost him after the creature realized his transformation was to the point where he had wings. He followed a real bat looking for somewhere to stay; Batman headed to the cave in hopes of synthesizing something to change him back.
Man-Bat found a cave to stay the night, but soon realized it was Batman's cave. Batman returned home and found him there. He was able to knock the creature out when he failed to reason with him. He worked to find a cure for Langstrom.

Marriage: Impossible!
Batman attempted to stop the Langstrom wedding (Man-Bat had escaped the cave before Batman could "cure" him). Francine told Batman nothing could stop them from getting married: Kirk had returned to their home that night. She couldn't bear to look at him, but she knew she loved the man inside. Langstrom refused to let Batman help him, but he gave Francine a way to prove her love. Batman realized what they'd done when she flew away from him.
Batman gave chase and eventually was able to dose each of them with the antidote he'd been carrying since Man-Bat escaped the cave. Both morphed back into human form and realized how terrible it had been to be "inhuman."