"Crown of Fear"
Commisioner Jim Gordon has been on the case of several disappearances; murders. All that is left when a body is found are skeletal remains, and whatever is doing this to people is still out there, and increasing the frequency of kills. He has had to turn to Batman for help, especially since the GCPD was tipped off to the possible involvement of Kirk Langstrom - the developer of the Man-Bat Serum.
Chasing Langstrom down in the Batplane, Batman recalls when he'd first met Langstrom as a man; a scientist. When the 900 block was affected by the spread of a man-bat virus, he sacrificed his humanity in order to save the innocents affected. Since then, though, Langstrom has continued to transform into the Man-Bat on a regular basis. All the same, Bruce feels a need to give him the benefit of the doubt in this case. In his encounter with the Man-Bat, though, Batman realizes that Kirk has given in to the serum; losing control to the creature's base aggression. From the hunger in his eyes, Bruce can tell that Kirk has already killed before. Even so, he calls out the man's name, hoping to coax the man inside out of the man-bat.
Three hours earlier, Bruce had determined that one of the corpses Gordon turned up had been killed not by a Man-Bat, but by an actual swarm of bats. However, no bat known to man is so meticulous as this in draining the blood and picking the bones clean of meat. Not even the most deadly species of piranha is as efficient. It is Bruce's hope that Langstrom can provide answers as to their nature.
Using a device that emits the low-frequency sounds of a sleeping bat-colony, Batman lulls the beastly side of Langstrom into dormancy, leaving the man in control. Seeing him this way, Bruce can tell that he is affected by physical dependency on the serum. Bruce insists that Kirk give up what remains of the serum in order to prevent any further damage, but Kirk responds that his repeated exposure to the serum has permanently altered his genetic code. He no longer needs it to transform - and neither does his wife.
In the ruins of the Caldwell Industries building, Batman and Langstrom discuss the events that led to Francine Langstrom - whose real name is Felicity Lee - becoming a monster. She was a corporate spy sent to watch and learn from Kirk in order to give up his serum to her employer as a biological weapon. She had used the wrong species of bat to create her version of the serum's compounds, resulting in her transformation into that weapon. Ever since she became addicted to the serum as well, she has been mutating into something even worse. She infected an entire colony of bats with her blood, and now they serve her. Kirk has tried to stop her, but he can't get through to her. So, he developed a counter-serum using a sample of her blood. Its effect would be a transformation back to human form - if only temporarily. During that time, she would be vulnerable. Langstrom already has a plan for how to bring her down, and Batman doesn't like it. He agrees anyway, though.
The pair of them meet outside the cave where she and her bat colony roost, and outside, Batman administers a sedative for Kirk, ensuring that he does not transform into a man-bat himself while they are trying to contend with another one. Using a sonic gun, Batman clears a path through the infected bats to where Kirk's former wife hides. When they encounter her, though, she rejects the names she used to go by, calling herself instead, the "Bat-Queen". She sends a swarm of bats to attack Kirk, and in the confusion, he drops the counter-serum, spilling it on the ground. Realizing that his plan has failed, Kirk begins to transform, and attacks her.
This would all be a failed plan, if the plan that Bruce had been using was Kirk's. Instead of the sedative he had claimed it was, Bruce had injected Kirk with the counter-serum itself. He had known that the syringe he'd given Kirk couldn't possibly penetrate Francine's hide, and hoped that the counter-serum could instead be transferred by something sharp enough that it could penetrate: the Man-Bat's teeth.
The plan succeeds, causing Francine to return to human form - but with the unpleasant side-effect that Kirk is now a monstrous creature in her place. Fortunately, Bruce manages to punch Kirk back to humanity, delivering both of the Langstroms to Arkham Asylum.
Upon his return to Wayne Manor, Bruce finds that his partner, Catwoman, is displeased to have been left behind for this mission.
"Crown of Fear"