Mark Lungo was kind enough to send me a copy of Glenn Leopold's script for Succubus!, a.k.a. "The Curse of Kataluna" (a name never mentioned once in the story). From what Mark tells me, the title was deemed too sexually suggestive, and by the time Hanna-Barbera had actually moved on to production of the episode, shortly before the series' cancellation, one assumes, the title would've been changed. As well as a lot of the dialogue, since the word succubus is mentioned a lot, and the villain's monster form is even called the Succubus.
On!
Okay, here is a rough description of the plot:
The story opens at the Megakat Shipyards, where dockworker Geno Furness and his pals are knocking off for the night. Geno turns down his coworkers' offer to go bowling and walks to his car, where he is attacked suddenly by a fierce gargoyle-like monster. Cut to the next morning, where Ann Gora exposits that the missing Geno is the sixth person to disappear in two months. Five other people have gone missing and turned up later on in dead, mummified states. She attempts to interview Commander Feral and Felina but is brushed off. The two drive to Enforcer Headquarters to find Callie Briggs and Mayor Manx waiting for them along with wealthy heiress Katrina Moorkroft.
We learn through dialogue between Callie and Felina that Katrina Moorkroft is a wealthy heiress who moved to Megakat City two months ago and donated a huge amount of money to the city. She expressed interest in meeting Commander Feral, and Manx, wanting to keep such a huge contributor happy, is there to play matchmaker. Feral finds himself smitten with Katrina pretty much instantly. She's an elegant, slightly older but still very beautiful woman (all females are called women by Glenn Leopold, incidentally; the word "she-kat" never comes up, although the word "tomkat" does) who wears a live ferret as a scarf. Feral gives her a tour of Enforcer Headquarters. Manx follows them everywhere, insisting on accompanying them to ensure everything goes smoothly and that Katrina is kept happy.
Felina hates Katrina on sight, while Callie is suspicious of her. Both women keep their comments to themselves. The feeling is mutual. Katrina is aloof and snobby towards Feral's niece but he doesn't seem to notice. He and Katrina decide to go on a date to the inaugural performance of the orchestra at the newly-opened Moorkroft Philharmonic, which Katrina owns. Callie decides to attend as well, so she can keep an eye on Katrina.
At the garage, Chance and Jake are working on Callie's car. We get another reason why Chance should never be allowed to tune up people's cars as he has insisted on installing "turbo accelerators" which cause the exhaust pipes to explode and detach, flying across the room, nearly hitting poor Jake. Callie arrives to pick the car up, and while they repair and reattach the exhaust pipes, she casually asks Chance if he knows about the philharmonic orchestra. He dismisses it as boring, so she asks Jake, and he likes classical music. She asks him to come with her to the performance, more so she can appear nonchalant (it'd look odd if she showed up alone). He agrees, and after they finish reattaching the exhaust pipes (making sure to anchor them more securely this time), she drives off. Chance angrily demands to know what he's supposed to do all by himself at the salvage yard, and Jake tells him he can fix the Turbokat engines, which have something wrong with them. This is apparently out of revenge for the exploded exhaust pipes almost hitting him earlier.
Elsewhere, Felina and the Enforcer Sergeant find the body of Geno Furness in the river. He's dessicated and mummified like the other five victims. Felina wonders when the gruesome nightmare will end.
At the Moorkroft Philharmonic later that night, Feral and Katrina sit in a private box. Mayor Manx is with them, having insisted on forcing himself along, but the two ignore him and schmooze over one another. In the audience below, Callie is with Jake, who is wearing a business suit. She keeps a close eye on Katrina, while Jake, oblivious, just enjoys the orchestra's performance. The music is being broadcast on the radio, and T-Bone is listening to it back in the hangar as he works on the jet. Angry over Jake getting to go on a date with Callie, and hating the music, he tunes (somehow) into an Enforcer band, considering listening to the Enforcers yack at each other more entertaining.
Meanwhile, at Skycor Towers, an apartment building that's under construction, a foreman gets attacked by the gargoyle creature that attacked Geno at the beginning. He runs and is attacked by a second creature. Felina shows up in a helicopter. The gargoyles attack her, shooting laser beams from their eyes. She calls for backup on the radio. In the hangar, T-Bone, because he tuned into the Enforcer band, hears her. Since the Turbokat's engines are still under repair, he takes the Thunder Truck. Back at Skycor, Felina battles the gargoyles in her chopper, allowing the foreman to get into a Jeep and drive away. However, Felina crashes into the partially finished Skycor building, and has to leap out of her chopper. The gargoyles zap the girder she's hanging off of, causing her to fall.
T-Bone arrives and rescues her and she takes up a gunner's position in the back of the Thunder Truck. The two pursue the gargoyles through the foggy night. The gargoyles chase after the foreman's Jeep and lift it into the air. One of them rips open the roof and yanks him out, and then they drop the empty Jeep down towards the Thunder-Truck, with T-Bone having to crash through a wall to avoid it. He and Felina recover and continue pursuing the gargoyles and their prisoner. The chase leads towards what T-Bone describes as the "high-rent" section of Megakat City, which is filled with mansions. Eventually, though, they lose the creatures and all they find of the poor foreman is his dropped hardhat in the bushes near one mansion in particular - Moorkroft Manor.
Deciding this is too much of a coincidence, Felina goes and knocks on the door, and speaks with butler Laszlo, who claims he hasn't heard anything unusual. Annoyed, Felina asks T-Bone to drive her back to Enforcer Headquarters. The two banter about what a great date they had, jokingly, and when he drops her off, T-Bone gives Felina what is described as a "SWAT Kat beeper," which seems similar in function to Callie's communicator (except with a blue button instead of a red one).
Back at the Moorkroft Philharmonic, the orchestral performance is over and everyone is heading home. Callie who I guess seems satisfied enough that not too much is untoward about Katrina, drives Jake home. Jake describes the performance by the orchestra as "radical," having really enjoyed it. As the car burns rubber, with flames coming from the amped-up exhaust pipes, Callie describes the tuneup job as "radical" in response. Nearby, Feral bids Katrina goodnight and she gets into her Rolls-Royce-like limo which is chauffeured by the stuffy Otto (described as resembling actor Erich von Stroheim). As they drive back towards Moorkroft Manor, Katrina begins to suddenly age at a rapid rate, pleading with Otto to drive faster and faster as she continues transforming.
By the time they get to the house, Katrina has completely turned into a withered old hag. She asks Laszlo if everything is ready and he tells her yes it is, so she goes upstairs. In a large observatory, the captured Skycor Towers foreman is shackled to a pillar. Katrina complains that the temporary rejuvenations aren't helping anymore, but she isn't worried, since by the time an upcoming eclipse happens, she'll be imbued with the lifeforce of the one who loves her and be beautiful again for another century. She approaches the foreman, and we cut to the outside of the mansion as bright light shines out through the windows. The foreman screams.
And I think this is a good place to stop.
I'm a writer okay? I need answers! 
