Chapter 1

"What are we going to do now?" Beckett asks despairingly, after Jim has departed, still completely discombobulated by the discoveries about his daughter and grandchildren. They'd offered to get him a car, but he'd said he thought he'd rather walk, to clear his head.

Beckett's not sure what head-clearing is required, other than a brain wipe, and even that would only last till the next time. Her terrible twosome haven't stopped shifting for a moment. Petra, always more determined and focused, is practising hard, and the sneezing is already diminishing in volume and vigour. This is helpful, in one way, since neither parent is that fond of constantly wiping snotty noses clean and mucus away. (The twins are also not fond of nose-wiping, but they don't get a choice in the matter.)

"I don't know," Castle replies, also looking at the twins. "Did you ever find anything that stopped you changing?"

"I wasn't looking, but nothing." She slumps. Castle comes and hugs her. "This is awful. We were going to start daycare, but that's out the window. We can hardly keep them inside 24/7, but what happens if you take them to the playground and suddenly there's two cats? Not good for the friendship groups."

"The children would love it."

"The other parents wouldn't," Beckett says crossly. "Just because you'd have loved it, doesn't mean anyone else would."

Petra discovers that being a toddler means that she can steal all the blocks from David-panther, who caterwauls loudly in complaint when he finds he can't steal them back with paws. He changes. Petra becomes a panther and swats his toddler form. The wails get louder.

"Stop that, Petra!" Beckett says. "You share the blocks." Petra turns her back. Beckett picks her up to eye level and stares her down. "You share, or time-out." Petra shares, recognising a stronger will than hers.

"That's not the worst of it," Castle points out gloomily, as Beckett returns to their joint floor cushion and nestles in again.

"Huh?"

"Mother, Alexis, Espo, Ryan, Lanie…"

"Oh, sh-oot!" There is a swift change of word there. "We can't never have them round."

"I can't not take the twins into the precinct to see you, either."

"Oh, God." Beckett considers the likely reaction of Captain Gates to two cubs, and does not find it good. She buries her face in Castle's shoulder. He pats her.

After a few moments, Beckett emerges. "I have an idea," she says gloomily.

"If it arrives in that tone, it's a bad idea," Castle points out. "Or a good idea that you hate."

"Yeah, but…like I said, we can't put the twins in an isolation cell." Though some days, when they are particularly badly behaved, it's a very appealing idea.

"We could take them up to the cabin," Castle suggests, "and teach them never to change without us telling them to."

"Castle," Beckett says with considerable exasperation, "even if they weren't your children" – he squawks – "toddlers have the attention span of a doped butterfly."

"I have plenty of attention span," Castle argues, and then drops his voice, "as you found out last night."

Beckett colours delicately. Castle had certainly demonstrated considerable and prolonged focus. She, on the other hand, had shortly been unable to focus at all.

"Even if we got it through Petra's head, David wouldn't remember past the first time he thought doing it was a good plan in his mind." She smirks nastily. "He's really very like you."

Castle grouses under his breath. Beckett sighs, still cuddled in. Astonishingly, the twins are playing co-operatively. That might, of course, be because both their parents are watching. She sighs again.

"Going up to the cabin's a good idea anyway. I've got some vacation days to take." She nods decisively. "Let's do that, too."

"Too?"

"Yeah." She returns to her deep gloom. "I never, ever wanted to do this, but – I think we need to tell your family and the team. And Lanie." She pauses. "And – er – Gates."

Castle goggles at her, boggled. This swiftly changes to consternation. "Beckett?" he gleeps. "All of them?"

"Uh-huh. And then we threaten them. Though if your mother ever mentioned it everyone would put it down to too much wine."

"True," Castle says, "but just a little mean."

He ponders for a time. While he does so, the twins are empirically testing the relative advantages of each form over a range of activities, which, as ever, rapidly descends into squabbling noisily and then fighting. Naturally, Petra is the first to discover that paws and claws are far better than hands for fighting, which equally naturally and much more rapidly lands her in time-out with a very stern lecture while David is being daubed with Neosporin and cuddled and fussed over until he stops wailing loudly.

"Oh, God," Beckett says wearily. "Is this our life now? Refereeing and para-medic-ing? Child Services are going to have a field day."

"If Petra wasn't just like her mother…" Castle says provocatively in revenge for Beckett's earlier comments on David's similarity to his father. He notices Beckett's distress. "Don't worry. Children do hit and fight. We just have to keep heading it off and dealing with it."

"Or add Petra to the precinct SWAT team," Beckett suggests. Castle snickers.

"Anyway," he says, letting David down from his arms and watching him toddle back to the blocks and toys, "you think we should tell Mother, Alexis and the boys."

"And Lanie" –

"Yes, okay, but why Gates?"

"Protection."

"Uh?"

"She can – er – leave out a few details, if necessary."

"Are you suggesting that our twins might get into trouble?"

"No," Beckett snips, "I'm suggesting that if they take after you they will get into trouble."

Castle fakes a wounded look. "Mean."

She plants a peck on his cheek. "There. All better."

"Kiss too, mama!" David demands, and gets one.

"Me!" Petra says, and also gets one. Castle gathers both twins into a bear hug and tickles them till they squeak. They happily go back to their toys and shortly there is noise and banging. Helpfully, the loft is soundproofed.

"I guess you've got some ideas about the order of – er – introductions?"

"Yeah. Gates first. We'll need her to whitewash any issues with the boys, and possibly Lanie. And she can arrest anyone else who's – er – difficult about it."

"So can you."

"Yeah, but it's better if it's not their parent."

"And then? After Gates?"

"Don't know. Seems a bit unfair that my dad knows and your family doesn't, but it's easier to keep my dad quiet. He's an attorney. He's used to confidentiality."

"Much as I hate to agree with that, my family is not used to discretion or filters."

"But she is a good grandmother."

"Gramma come," Petra instructs.

"My Gramma," David argues.

"NO! Mine!"

"Mine!"

"Grandma is for both of you. Share nicely."

"NO!" the twins yell in unison.

Their parents sigh. "Time out?"

"Guess so."

The twins separated, or possibly caged, for a moment or two, Castle and Beckett consider the unhappy necessities of the next few days.

"Gates, then Alexis, then Mother, then the rest, all at once."

"Yeah. Ugh," Beckett agrees, sunk in deepest gloom.

Gloom is not relieved by the twins being returned to the family room and smothering her in sticky fingerprints, scattering small blocks on which she will undoubtedly stand late at night and have to suppress her swearing, and implanting sloppy, soggy kisses and hugs. Sweet as it is, there's only one person with whom she wants to exchange bodily fluids, and he is not two. Toddler affections have no discretion at all.

"Monday is not going to be any fun," she grouses.

"Monday?"

"No point delaying. Erm…. I'll give you a call when I've looked at her schedule so we can deal with Gates. I think you should bring the twins… they're cute, and she quite likes them."

"As much as she likes anyone," Castle humphs.

"Just because she doesn't like you…" Beckett notes, idly. Castle growls. "C'mon. Let's get the terrorists fed, bathed, and into bed." Suddenly she grins widely. "If they're not synced any more, I can be Onyx whenever I like!" Castle's answering grin lights up the room.

The next day, Beckett sneaks a look at Gates's schedule and discovers that she is free, or at least does not have meetings with 1PP or any other important personages, at the end of Monday.

This is good, and even better, the boys will have gone out interviewing and will be missing until the next day. It means that Castle and the twins can leave with alacrity when it inevitably all goes horribly wrong. Gates's reaction will probably be rather less reasonable than that of Dr Maine, and a quick escape may be required. There will be considerable acerbity. Gates is not a people person, and it seems entirely reasonable to assume that she is also unlikely to be a pet person. Even if she were, Beckett has yet to meet anyone who claims to be a panther person.

At five on Monday, Castle texts to say that they're about to come up. Beckett tells him to make it really, really quick, before anything more can go wrong, and then, when they arrive, astonishingly all human, knocks extremely rapidly and trepidatiously on Gates's door before anything dreadful can happen.

"Yes, Detective Beckett?" Gates says, regarding her with a chilly stare which has not abated in almost four years of working together. For a given value of working together, that is, which does not encompass friendship, though it has become mutually respectful.

"Er, we" – Gates raises an eyebrow at the unexpected sight of Castle and the toddlers within her sanctum – "need to talk to you, sir. Privately, sir." The eyebrow lifts further as Castle shuts the door, and puts both twins down. This, happily, removes them from Gates's immediate field of vision.

"If you wished to tender your resignation, Detective Beckett, I assure you that you did not need either Mr Castle or your children to protect you. I should, of course, be extremely disappointed."

Beckett's jaw drops, on account of both statements. "No sir. No. Not resigning. Um… Castle and the twins aren't here to protect me."

"And one assumes that you are not pregnant, either, since that would not require your entourage."

"No!" Beckett emits, horrified.

"So why have you planned this expedition? Surely even Mr Castle's offspring do not require me to bring down the force of the law upon them at two years old?"

Beckett twists her hands. "Sir, um – Castle, close the blinds, please" –

"What?" snaps Gates.

"Um… I… we… have a genetic condition."

Gates suddenly acquires a small hint of concern. "You do? You and the children?"

Beckett looks down. David is still a toddler. Petra is not, and worse, is sneaking stealthily towards Gates's ankles. She'd better get this out quickly.

"All four of us. And… er… with the twins getting older it's beginning to be difficult to hide it."

"There is no medical condition on your personnel record, Detective," Gates points out coldly.

Petra takes another prowling step closer. Captain Gates's shoes have a neat tassel on them, which is swaying enticingly.

"No. Um… Sir, I'm a shapeshifter. We all are. And the twins aren't synced to me any more so we can't hide it."

Gates stares at them. "Are you insane, Detective?" she emits, freezingly.

"She sounds just like Dr Maine," Castle points out.

"A doctor?" Gates forces out in a strangled gasp. "A doctor helps you maintain this delusion?"

"Um… I think you'd better move your feet," Castle says to Gates, spotting Petra.

"I think it would be better if you moved yours," Gates snaps. "Right out of my office – Holy Mary Mother of God!"

Beckett, deciding to slice through the inevitable outrage and disbelief, is now Beckett-panther. Petra is one scant baby pounce away from Gates's shoes when Beckett growls and she comes skittering back. Castle picks her up. Gates appears to be praying. So far she has prayed to the Holy Trinity, the Twelve Apostles and more saints than Beckett had known existed. She'd never realised that Gates was religious. Then again, a full size panther appearing in your office could make anyone religious.

"Captain Gates," Castle says, "please would you open your eyes? This is Petra. You've seen her before. From a distance, admittedly, because it's not like you're really very keen on any of us or anyone else so we didn't bother you but" –

"Be silent, Mr Castle."

Petra, taking offence at the tone, attempts a growl, and receives in return an icy glare. She squirms and wriggles in Castle's arms and turns back to a toddler. Fully occupied with Petra, Castle fails to notice David toddling over to Captain Gates. David, unlike Petra, regards the world as populated by friends whom he has not yet met, despite all too frequent rebuffs. Beckett, who is regarding Captain Gates's frozen face with abject terror despite her claws and sharp teeth, likewise fails to notice the imminence of disaster in the form of David.

He plants both, undoubtedly sticky, hands on Gates's well cut suit, and looks adorably up at her. "H'lo," he says. "Mama a cat." Gates directs her glare at him. David resorts to measures which worked on his grandfather, and becomes a very cute black kitten, with bright blue eyes. He leaps up into Gates's lap. Instead of the petting he clearly expects, Gates picks him up by the scruff of the neck, regards him beadily, and places him on the desk in front of her. He extends a tentative paw in her direction.

"Sit still," she commands. David becomes petrified.

"Wow!" Castle says. "Even Beckett can't do that. Have you thought of hiring out as a nanny? I'd pay a fortune for you" –

"Mr Castle. Just over four years ago, against my better judgement and wishes, I took over this precinct, rather than remaining with Internal Affairs, following the death of Captain Montgomery. Since then, also against my better judgement, and certainly against my wishes, you were permitted to return to shadowing Detective Beckett. I have always considered this to be a mistake, although you have to some minor degree proven useful. Your usefulness, however, is entirely dwarfed by your capability to cause complete chaos." She takes a very chilly breath, and continues before he can protest. "Now I find that my senior detective is a supernatural impossibility, and, as ever, you are at the centre of events."

"Why does everyone think I did it?" Castle complains.

"Dada did it," Petra says happily. Gates regards her with disfavour. So does Castle.

"It wasn't me," Castle says plaintively.

"It wasn't," Beckett says, changing back. "I was a cat long before I ever joined the Academy."

This does not appear to improve Gates's mood.

"My precinct does not require supernatural assistance."

"Are you firing me, sir?" Beckett enquires tightly. "What reason will you give 1PP – or the court, when I sue?"

"No, I am not firing you – I said stay still," she directs at David, who squeaks and cowers.

"Dada did it," Petra says again.

"Shush!" Beckett tells her.

"I note that your children are as ill-disciplined as their father," Gates says, "although they, at least, have the excuse of childhood."

"My children," Beckett snaps, heedless of rank, "are a lot better behaved than you've just demonstrated."

"Nasty lady," Petra says.

"Quiet," Beckett tells her. "Say sorry. You were rude."

Petra looks very like she's about to say no. Then she regards her mother's face. "So'y," she says.

"As am I, Detective. I should not have said that."

Beckett thinks she hears in front of any of you, and lets it go.

"So. Yet again, Detective, you and Mr Castle have presented me with a problem. Explain why I should be concerned with any of this?"

"Until Saturday, sir, the twins were synchronised with me. If I was human, so were they."

Gates regards the kitten on her desk and the toddler in Castle's arms with some irritation. "I see. Clearly this is no longer the case." David tries a surreptitious prowl towards an interesting figurine. "Please remove your kitten from my desk. Your husband destroying one of my collection of rare dolls is quite enough."

Petra looks like she's thinking of saying Dada did it again, and receives another searing glare from her mother.

Beckett removes David from temptation, with an expression very similar to that she uses when trying to stop Castle doing something dumb. Or heroic, which often seems to be the same thing.

"We thought," she carries on, "that informing some carefully selected people might help us manage the situation."

"Should I be flattered?" Gates enquires. She does not sound flattered. Appalled might just about cover it. "I can think of no reason to involve me in this" – she searches for a word – "debacle. My precinct should be run in an orderly fashion, which does not involve children or shapeshifting. I would prefer it did not involve Mr Castle, either." The accent on shapeshifting conveys absolute abhorrence.

"Sir, given the choice I don't think any of us would have been a shapeshifter."

"I would," Castle says. "It's totally cool."

"I have no doubt that you would think so. However, your preferences are entirely irrelevant to this discussion." Castle subsides, squashed.

"Sir, the fact is, we are. You might not like it" –

"I don't. Is that not obvious?" –

"but it's true. And we need your help. Or at least your silence, because" –

"Because you can't afford to let this be known. Tell me, Detective, how long has this been going on?"

"Me? Um… since I was nineteen."

Gates goggles. "You have been a panther since nineteen?"

"I didn't realise till I was twenty," Beckett says, not that this appears to help anything. "And no-one at all knew until six years ago, when Castle worked it out."

Castle preens. Gates does not look impressed. "That may explain your children," she says coldly, "who may indeed deserve some protection. It does not explain Mr Castle."

"She changed me. She bit me and then" –

"Shut up, Castle."

"Biting naughty," Petra says, in saintly tones which bear no resemblance to her personality, or indeed her distressingly frequent actions.

"Shush!"

David wriggles in Beckett's grip and becomes a toddler. Gates emits a squeak, then recovers. She raises her eyes to Heaven.

"You thought it was a good idea to change Mr Castle," she says flatly.

"I asked!" he says.

"You whined," Beckett says tartly.

"Be quiet," Gates says, and all four of them are. "So. All four of you are shapeshifters, which, until today, I was unaware had existence outside of a niche genre of so-called literature. I assume, from the evidence of the last few moments, that you are all both panther and cat. And, for some reason which you have yet to disclose, you believe that I am both in a position to assist you and that I would actually do so."

She fixes them with a glare. "I do not appreciate you springing this upon me. However, I will not dismiss it out of hand. I shall consider. When I have finished, I will let you know. In the meantime, do not bring your children to the precinct. Mr Castle, you and the twins may leave." That is most definitely an order. "Detective Beckett, remain."

Castle casts her a look of sympathy, collects both his toddlers and achieves the elevator in nothing flat, before anything awful can occur. Beckett quivers.

Thank you to all readers and reviewers.

Yes, this is another insane instalment in the Cool for Cats universe, as if that weren't perfectly obvious. This is the responsibility and fault of a combination of Shutterbug5264 and BigKahuna, who each wanted to know what would happen when the twins weren't synced any more. All complaints of contagious craziness should be directed to them.

13 chapters. Sun/Tue/Thu schedule, unless otherwise advised.