On a snowy night, some dockworkers unload fruit when suddenly a bat creature attacks, guzzles down several fruits, and flies off. Suddenly Dr. Kirk Langstrom, who once transformed into such a creature, wakes up from a nightmare. His wife, Francine, asks if something is wrong, but he shakes his head no. Kirk gets up for air and suddenly sees fruit and claw marks on the carpet...
Back at the docks, Batman overhears the men reporting the attack to the skeptical police and immediately suspects Kirk. The next day, a worried Francine asks her father, Dr. March, about Kirk, and he says he has been holed up in the lab all morning. Francine goes in to see Kirk working on what he claims is a cure. Batman arrives shortly and Kirk denies having taken the formula deliberately. Francine runs out in distress and Kirk blames Batman, thinking his antidote didn't work.
Batman takes a DNA sample from Kirk and leaves. Suddenly, the Man-Bat attacks him and gives chase. Batman fails to subdue the creature, but manages to get a hair sample. Having compared the two DNA samples, Batman approaches Kirk with the news that they don't match—the antidote did work, and there is a new Man-Bat.
Batman investigates Dr. March's files and March catches him. March reveals that he created a new serum, still convinced that only a man-bat could survive an evolutionary cataclysm. However, Francine walked in and March dropped the formula in shock. Suddenly, he realizes that Francine was infected with the serum when she tried to help clean up. Before leaving Batman says, "Is that what it's going to take? Your daughter's life, before you end this insanity?" Seeing the error of his ways, Dr. March burns his research.
Francine has left Kirk, unable to deal with the madness, but Kirk is aboard the plane she is taking and reveals he isn't the creature. Francine gets a headache and heads for the bathroom where she transforms into the She-Bat. She breaks open the plane door and grabs Kirk. Batman arrives in the Batwing, but first he must save the stewardess and close the plane door.
The She-Bat carries Kirk to a bridge tower and fights Batman, who injects her with the antidote. After transforming back to Francine, she almost falls off the tower, but Kirk saves her.
Tropes in this episode include:
- Body Horror: The bat-monster transformation. Worse than in "On Leather Wings" because of this victim being entirely unwilling, and indeed unwitting.
- Catapult Nightmare: Kirk apparently woke up from a nightmare where he's the Man-Bat again. But soon finds that it may not be a dream at all. Only it actually was.
- Dramatic Irony: Kirk meets up with Francine to tell her he's not the Man-Bat and it doesn't matter who is. Except it does, as he finds out Francine is the She-Bat.
- Explain, Explain... Oh, Crap!: Dr. March explains how he wanted to recreate the Man-Bat formula, only to drop the beaker when Francine walked in on him working. He recalls how she helped him clean it all up—and then cut her finger on the glass, with all the chemicals surrounding it.
- Exposed to the Elements: After Francine reverts back to human form, she was clad in only a torn sleeveless blouse, torn pants, and barefoot while on the snow-covered bridge tower.
- Foot Popping: Francine, when she hugs Kirk at the end of the episode.
- Foreshadowing: Francine runs away while Batman and Kirk argue over the reappearance of the Man-Bat. She appears to be distressed over it, when it turns out she's beginning to transform into the She-Bat due to the frustration.
- Jekyll & Hyde: Francine seemingly more so than Kirk, as she seems less aware of what's happened to her when transformed into the She-Bat.
- My God, What Have I Done?: After Batman hammers home that Dr. March's research has endangered his daughter's life this time, he burns all of his notes and hangs his head in shame.
- Not Me This Time: When the Man-Bat is spotted once more, Batman naturally goes right to Kirk Langstrom to examine him. Of course, it turns out that this time, he really is innocent.
- Rage Against the Reflection: Francine Langstrom does this when witnessing her transformation into Man-Bat in the mirror of an airplane bathroom.
- Red Herring: Francine's father listens in on Kirk and Batman's conversation, and walks away quietly. It's not entirely a red herring however, as he is responsible for the reinvention of the mutagen.
- Sequel Episode: To "On Leather Wings", concluding the Man-Bat storyline.
- Skyward Scream: The She-Bat unleashes a sorrowful one on Gotham Bridge after setting an unconscious Kirk down.
- Vapor Wear: Different from the Man-Bat's previous appearance—and absolutely all of his appearances in the comics and other media—this one has on a torn-up shirt most of the time (except at the beginning, when Kirk is still the prime suspect). This conceals that this Man-Bat is actually a She-Bat. Its rather flat torso is still visible, but the remains of the shirt are adequate cover for Francine when she transforms back at the end.
- Was It Really Worth It?: Once Batman and Dr. March realize that Francine is the new bat creature, Batman lays it in on him on what his continued research has caused. He angrily asks March if the life of his daughter is what it will take to end the bat serum research.
