Chapter 1

"I got you a present," Castle said happily.

Beckett, in her preferred Onyx-form for curling up in Castle's excellently comfortable lap or draping herself over his shoulder, looked up, saw nothing except a small container, flicked her tail disdainfully and returned to the far more important task of washing a paw. She'd had a headache all day and now that she was home, with the delightful prospect of having the following day off, being Onyx soothed it.

"C'mon. Change back." He picked her up, plopped her on his shoulder and sat down on the couch, stroking her silky fur. "You'll like it."

She purred, and snuggled furrily into his neck. She didn't want to change back. Castle should change, and then they could be very happily feline together: her slim Siamese nestled into his much larger, heavier Maine Coon: their black fur merging and their tails entwined. That would be a much better plan than some small box containing an indeterminate substance. Or he could keep stroking her, or even better, play with her ears or brush her, to leave her in a post-orgasmic haze. That would solve the headache. She mewed commandingly.

Castle put her down and bounced off the couch, leaving her behind. He was not allowed to do that. She jumped down, and stalked after him to the kitchen, where he was putting the kettle on. What? He was reaching for a teapot? No, no, no. She drank coffee. Tea was for other people. And now he was opening his little box, which contained tea leaves? That was not a present. That was a mistake.

She stalked back to the couch and concentrated on washing her paws, extending and retracting her claws to ensure that they were properly polished and functional. There was the clonk of a tray on the table. Steam rose from the teapot's spout, and wound its way through the air to her sensitive cat nose. She drew in the scent. It was...interesting. Appealing. She padded on to Castle's lap, to take a deeper breath.

"C'mon," he said again. "I got it specially. I had to go all the way across town to a specialist tea shop for it. It's called Nepeta tea. You'll like it."

That did sound intriguing, and he'd gone to a lot of trouble, and, well, how difficult was it to make him happy? She stood up on her back paws, butted her head into his neck, and changed, to end up sitting on his lap and neatly nestled in.

"Nepeta?" she queried.

"It's a herbal tea. Supposed to be good for headaches, and you've had a pretty stressful week, so I thought it might help. Mother used to swear by teas to cure headaches – on other people. She used Bloody Marys."

Beckett snickered, then snuggled in further and kissed his neck. "That's really sweet, babe. I'll give it a moment to cool down, and then try it." She looked at the tray. "Aren't you having any?"

"No. I got it specially for you – and I tried a tiny bit of it in the shop and it was nice but I thought you needed it more, so I got myself some camomile tea." The small kettle clicked off. "I'll just infuse mine."

She – reluctantly – slid off his knee and allowed him to make his own small pot of tea. She thought he was a little expectant, but Castle was ridiculously fond of giving her silly little gifts as often as he could get away with it, and he always wanted to see her reaction to them. (She didn't give him silly little gifts. Instead, every so often, she bought him flowers: showy peonies, when she thought he needed a little flamboyance boost; heartsease if he was a little unhappy or had received an unkind review; crimson roses just because she loved him with all her heart. They were rarely without flowers somewhere in the loft.)

She waited for him to return, and then curled back into his lovely broad chest, enclosed in a lovely strong arm, and perfectly, felinely, content with life. Castle hummed happily, and poured his own tea.

She sniffed deeply – it had a really nice scent – took a cautious sip – a burnt tongue was so limiting – and regarded the teacup with astonishment. "This is really nice." Castle smiled happily. She took another deep breath and a mouthful, and savoured it. It was very good indeed. She snuggled more firmly into Castle. He was delightfully snuggly, and she should definitely take full advantage of his snuggliness, accompanied by another mouthful of tea.

In fact, she should just slither back into his lap. After all, it was right there, beckoning her. It looked very comfortable. And if she were in his lap, he'd be much more kissable. His lips looked very kissable, suddenly: even more so than usual. Conveniently, he put his cup down, and she instantly slid on to his knee and tucked her head into his shoulder. Even more conveniently, she could smell his quite delicious cologne, and nibble at his neck, and then leave a trail of little peck-kisses all the way up to his jaw. She should spend lots of time kissing Castle. Lots and lots and lots of time.

"Why aren't you petting me?" she pouted, pettishly. "I like being petted." He should be stroking her hair, and tucking it behind her ears, and generally fussing over her and fondling her and just plain petting.

"Sure," he said easily. "C'mere." He glided one large hand over her hair, down to her back, in just the way she liked best, and she arched her back into the touch and half purred, even in Beckett-guise. She also wiggled a little. "Do you want your tea?" She certainly did. She liked this new tea.

"Yes, please. It's really good."

Castle handed her the cup, and she drained it and put it down. It was warm all the way down to her tummy... huh? She never used the word tummy. It should only ever be applied to children, and there certainly weren't any of them around. Good. The existence of children would definitely cramp her style. Thinking of which, why was she leaning on Castle's extortionately expensive, but stylish, button down when she could be nicely nestled against his nice warm skin? She opened a button or two, and laid her cheek on said nice warm skin. Quite without her conscious input, a few more buttons opened, which left a nice space into which her hand fitted perfectly. It slid round his middle, and he squeaked.

"You tickled me! That's not nice!"

Beckett giggled. Indignant Castle was always very funny. She tickled again, just to see what would happen, and then had another idea. She became Onyx, turned round, and wriggled her tail into the space in the shirt. Castle positively squealed.

"Stoppit!" He most unfairly plucked her out, disarranging her tail fur, and plopped her back the other way round. She stretched up to lie on his shoulder, and used her tail to tickle his nose. He sneezed, and squeaked more. "Stop tickling me!" She would. If properly encouraged. He hadn't petted her properly and she wanted petted, and fondled, and ear-caressed. She flicked her ears at him. "Oh, I see." About time, Castle. He stroked around her ears, and she settled down and purred happily until his clever, naughty fingers reduced her to a cat-shaped puddle of satisfied sensuality.

Still. She wanted rather more, and suddenly she knew exactly how to acquire it. Her tail trailed insinuatingly over Castle's stomach, and wriggled just under his belt. His eyes widened. "Beckett..." he whimpered, "what are you doing?"

"If you don't know," she husked, changing back, "then I'd better show you." Her fingers replaced her disappearing tail. She wondered why she'd never teased him with her tail before. It had certainly had a most interesting effect. She changed back again, suddenly. How had that happened? She hadn't meant to.

"Ow!" Castle yowled. "Claws!"

She pulled her paw out of his pants. She certainly hadn't meant to extend claws there. She changed back to Beckett.

"Sorry," she said. "But if you took them off, it wouldn't have happened." What? She hadn't meant to say that. Castle stared at her. She stared back, with her best glare, used fingers to open his pants and changed back to Onyx. Her tail drifted over him.

"I thought we agreed same form only?" he squeaked.

Rules were for other people, though she certainly didn't want mixed form sex. Eurgh. Some indecent teasing, however... Her tail flickered. Castle whimpered, again. She stopped tickling his assets and pushed herself into his lap, squirming on to her back and rolling over and over.

"Beckett, are you okay – oh my God."

She'd leapt down and was now happily rolling round the floor, mewing loudly. Why had she never done this before? It was as good as ear fondling or brushing. She rolled some more. The rug felt wonderful on her back. She lay on her back, wiggled orgasmically, and waved all four paws in the air. Despite her open invitation, Castle monumentally failed to tickle her tummy – hold on a moment, there was that word again... oh, who cared? She wiggled around the rug again, and then spotted Castle, still sitting stump-like on the sofa. She wanted her tummy tickled and her ears petted and her fur brushed.

She wouldn't mind some more of that excellent tea, either. And after that, Castle could do something useful and strip. Slowly. After that, she was sure she could think of something for them to do – oh look, she could see a moth! She bounded over to it, chasing it round the room but never quite catching it, which was totally unfair.

Oooohhhh! Tail! She followed the end of the tail around, but every time she tried to jump on it, it ran away. That was totally unfair, too. It should stay put and be pounced upon. Tail-chasing was fun. Playtime! Even if it was unfair that the tail wouldn't play nicely.

Equally unfair, Castle had caught her and stopped her playing. She didn't get nearly enough time to play, and he was spoiling it. Well, she had a solution to that too. He shrieked as she turned into her panther and growled at him.

"Don't growl," he said. "I wanted to pet you, and you're growling at me. It's not nice."

Oh. Petting. Yes. She'd wanted petting – ooohhhh, a bit of his shirt was flapping! She pounced on it.

"Yee-ouch!"

Oh. Ooops. Oh dear. She looked at him penitently, still a full-size panther, and licked the scratch in his side to make it better. She was tired. Maybe a nice nap would do her some good. She lay on the couch with her black head on Castle's lap and closed her eyes.

Castle stared at the sleeping panther and wondered what the hell had just happened to her. She'd drunk her tea, which he'd bought because she'd been really stressed lately and the shop had said it was excellent for headaches, and then she'd gone totally insane in all three forms, and now she was asleep.

Rather too late, he Googled the name of the tea.

Oh, shit. He should kill himself now, because Beckett was going to do it for him just as soon as she had worked out what had gone on. Oh, shit. He'd accidentally got her high. Oh God, he was so dead. He'd never thought... and she was human when she drank it... and oh God he was dead.

He'd given Beckett catnip tea.

Oh God.

He hadn't meant to. He really, really hadn't.

She wasn't going to believe him. Oh God. When she woke up there was going to be hell to pay – or Beckett, which was worse. Oh God.

It occurred to Castle that if he were his full size male panther, Beckett probably couldn't kill him. At least, not if he covered her and pinned her down. In any form, she couldn't defeat his massive panther. If he stayed human, she could kill him in dozens of ways from all three forms – even Onyx could kill him, with a well-aimed slash of her claws, if he didn't get her wrapped up first.

Oh God. He'd doped her. He frantically looked up the effects of catnip – and why had the tea store not identified it properly? It wasn't fair that they'd hidden its true name – and found that Beckett was pretty much a textbook case. Oh God.

He looked down at the sleeping still-panther Beckett, and frantically wondered what to do to save the situation – and his testicles, and probably his life. Even so, he automatically stroked her silky fur, which was soothing. She purred in her feline sleep, and twitched. He cuddled her, and wished very strongly that she were in Onyx-form.

A while later, Beckett's panther eyes opened: hazy and definitely not (yet) murderous. She made an odd noise, as if she were trying to talk: neither a purr nor a growl, certainly not a miaow. Panthers, Castle had learned, did not miaow.

"Hey," he said softly. Her head shook, as she tried to clear it. Suddenly there was human-Beckett, with her head in his lap.

"Urrrggghhhh," she said. "What happened?"

"You fell asleep," Castle said very disingenuously. "Are you okay?"

"Urrgh," she said again, and sat up, shaking her head some more. Castle waited nervously.

Slowly, remembrance slunk across her face, and she shrank into herself and blushed violently. "What did I do?" she wailed. "I never behave like that." She turned into Onyx, and jumped down on to the floor to hide out of sight and wash her paws frantically, radiating sheer embarrassment.

"It was cute," Castle said without thinking. "You're really cute when you're playful." Onyx's paw washing intensified. He leaned over to check where she was. "C'mon. Come back here and be petted." Onyx didn't move. She'd also stopped washing her paws, and her ears and tail were twitching – oh God, that pattern of twitching always indicated intense thought. He stood up, under the guise of putting the tea tray in the kitchen. If he were quick, he'd make it to the bathroom – which locked – before he was found out.

He got two steps. Onyx growled, and suddenly the panther was between Castle and the bathroom. He walked to the kitchen, stalked by Beckett-panther, and was then herded back to the couch. She didn't look at all friendly, and her claws flexed. He sat down, hurriedly. The panther changed back to Beckett, who drilled him with a most unwelcome glare.

"What did you do?" she interrogated. He cringed. "You put something in my tea, didn't you? That's why you were so keen on me drinking it. You spiked it."

"I" – she rolled over him before he could say didn't.

"It's just like you made fun of me with t-shirts. Well, if you think that's a funny joke you'll like this one even better – I'm going home."

She slammed out the door before he managed to open his mouth, and by then it was too late to change to stop her. He grabbed his jacket and dashed after her, crashing down the stairs and out into the street.

She wasn't there. He couldn't even see a space in the crowds where she would have forced her way through them. Castle, unwilling to leave the quarrel – no, Beckett's unjustified jump to a conclusion which simply wasn't fair – to fester, took himself to her apartment and slithered through the cat-flap. She had plenty of books and coffee to keep him occupied until she arrived.

Beckett had exited Castle's building, slipped into the alley close by and changed to her cat again, leaving herself invisible in the gloom. She sneaked through the crowds till she reached another convenient alley, returned to her human self, and caught the subway to Central Park. Some soothing squirrel-murdering was just what she needed.

She disappeared into the dark by the entrance, and Onyx skulked into the dusk. In an hour or less, the panther would come out to play, safe from passing joggers. Lowlifes would not be safe from the panther, however. She growled, and the local wildlife took off for safety. Onyx curled up at the base of a tree, and waited for darkness to fall, eyes shut, tail curled in.

Her calm position didn't translate to her mood. It was typical. He couldn't resist his dumb research whether it suited her or not. First t-shirts, and now tea. Well, she might research some T as well. Torture, for a start. She cringed again at her earlier behaviour, even if she had been doped. She'd really thought he'd stopped that sort of dumbass prank. She hunkered down again, and gave thanks that cats didn't cry.

Not long later, a trail of disembowelled squirrels and pigeons showed her infuriated path. Sirens squealed as those few lowlifes who inhabited Central Park on a cold March night found something a lot more dangerous than they were, and didn't like it one bit. Fortunately, the Central Park precinct was delighted to assist them to a safe place, though its facilities were basic and the locks were on the outside of the rooms.

Hours later, the panther's blood lust and Beckett's furious temper were sated. Her hurt and disappointment were not.

Castle waited, reading. A third book finished, he looked for a fourth and realised that it was long past midnight. It didn't reassure him. He hadn't eaten: he didn't want to eat. He simply wanted Beckett to show up so he could make her listen to him. He understood where she was coming from, but she was wrong. He'd never deliberately have got her high. Never.

He had an idea. He was tired, anyway. He tucked the book back into the stuffed shelves, switched off the lights, and changed into his Maine Coon form, curling up on the couch. In the dark, he'd be invisible. He reckoned Beckett would go straight to her bedroom when she eventually came in – and what was she doing, anyway? Probably the precinct – that was her go-to refuge. He should have gone there... she couldn't kill him or change in public. He tucked his head into his paws, his wide tail around his body, and dozed.

He was woken by Beckett coming in, and, as he'd predicted, going straight to her bedroom: hard, fast clicks on the wooden floors. Castle-cat didn't move. He'd give her some time to get into bed and then...um...take steps. He plotted carefully: first, pad silently into her room, then, still as a cat, curl up next to her; if she woke, become the massive panther until she would listen to him. She only said she slept with a gun. She didn't really – at least, she never had when he was there.

His sensitive ears picked up the rustle of her quilt, fading into even breathing. He waited for several more minutes, then, quite certain she was asleep, ghosted into her bedroom. He changed to the panther, and surveyed his prey.

Oh, fuck. She'd been crying. Guilt stabbed him. He hated when she cried, and hated more that she only ever did it when she thought he wouldn't find out. Of course he always did find out, but... she hid from him, rather than leaning on him. Six months in, and (even though she'd admitted she loved him already) she was good at sharing happiness but no good at all at sharing anything that might indicate weakness: still fighting to pretend that she was invincible. She didn't need to. He loved her anyway: all her little foibles and fretfulnesses, and he'd love her even if she sometimes needed support. He'd love her whenever she needed support.

Thank you to all readers and reviewers.

More insanity in the Cats universe, prompted (again) by Bahamut Slayer. Two shot.