Disclaimer: The only part of Castle that I own is the TV on which I watch the show.

A/N Time warp! My apologies: In the first chapter I should have said that the previous body-doubles case was 15 months ago and that Alexis came back from Costa Rica a year and a half ago. Apparently my brain is frozen in 2104. It should thaw out eventually.

She is banging her forehead hard and harder on the steering wheel in an odd but regular rhythm—10/4 time, like "Say a Little Prayer," which is exactly what she's doing, saying a little prayer. God help me, God help me, God help me. Her hands are clutched so tightly that they're cramping, but she is so overwhelmed that she's unaware of this external, self-inflicted pain.

"Detective! Detective Beckett! Beckett!" LT, who had been cutting through the garage on his way back from lunch when he saw her, is knocking on the window, but she doesn't react. Afraid that opening the door of her cruiser will freak her, he unclips his flashlight, turns it on and taps it lightly against the hood, aiming the beam at the wall rather than the car's interior. Beckett is keening like an animal caught in a trap. It's a sound he has never heard coming from a human, but she's still not responding, and now he's pretty freaked himself. Just as he decides he should go for help, she turns her head and looks directly at him. She blinks, and blinks again, slowly.

"LT?" She speaks his name like a question, as if she's not sure that she recognizes him.

"Yes, yes, I, oh. Detective Beckett, yes, oh, are you all right?" He's stumbling. He has no rulebook to follow, no clue how to handle the coolest, most controlled person he knows when she is melting down like this. Melting down on police property. In police property.

Beckett stiffens her spine, takes both hands off the wheel and puts them in her lap. She can do this. She can carry it off. She can steady her voice. Rolling the window down with her left hand, she lifts her right, palm out. "Excuse me, LT. I'm so sorry. That was really unprofessional of me and I'm sorry that you saw it. I'm fine, really. I'm fine. It's the case, you know? Just this case. Kelly Nieman. She hit us so close to home before, with Dr. Parish and Espo, and she's back." She shudders softly. "I'm on my way to interview her."

"You sure you're OK?"

"Absolutely. See?" She holds up both hands, and there's not a sign of a tremor, but it has taken everything in her to keep them still. "LT, could I ask you a favor, please?"

"Anything, Detective."

"I'm really embarrassed that I lost it there for a minute. If you wouldn't mind keeping this between us, and not telling anyone upstairs, I'd really appreciate it."

"No problem. You got my word."

She smiles gratefully, turns on the engine, and waits to make sure that he boards the elevator. Giving him a small wave, she drives away. As soon as she's out of sight of the precinct, she pulls the car over until she can control her breathing, calling on every suggestion that Burke ever made to her. She has never been this frightened: not when she watched Castle rip wires from a time bomb or stood on one herself, not any of the times when he or she, separately or together, had stared into the red maw of death. Nothing, they were nothing compared to this. Castle's daughter had gone, and they hadn't even known it. And now her eerie replacement, her manufactured doppelgänger, is here in her place.

It all makes nauseating, flesh-crawling sense now. The defiance, the belligerence that Alexis deployed, everything designed to distance herself from Castle emotionally and physically so that he couldn't track, from day to day, the little things that weren't quite right. The details she didn't remember; the slight shifts in her taste in food and clothes, music and movies; the switch away from pre-med at Columbia. Taken individually, they were insignificant, the typical changes of a young woman wanting to make her own way in the world, to pull away a bit; bundled together, they were something else completely, a paradigm shift. How had she missed it? How had he? The reasons stacked up like dirty plates in a sink: because they had been in their own rosy world; because they had been consumed with planning a wedding; because the wedding was sabotaged; because Castle was abducted and she was out of her mind while he was gone. But also because the "new" Alexis, the ersatz Alexis, had been inching back, had grown closer to the original since the spring. She had used her carefully crafted time to observe and absorb and finally to put on, like a beautiful made-to-order coat, a life that was not hers.

What had Kelly Nieman sent her version of Alexis to do? What was she poised to do? Kate, bathed in terror and awash with guilt, had to decide, within minutes, what her short- and medium-range plans were. The long would have to wait. The immediate challenge was not to tip her hand to Nieman but still to confront her about the death of a young woman who was the double of another. Pam Hodges all over again. Her next problem was whom to confide in about Alexis, about her suspicion—no, her certainty—about Alexis. This was far more more brutal, this cut through the heart and through the bone. She cannot tell Castle first, can neither bring him to his knees nor raise him up with false hope if there is not a breath of a chance that his Alexis is still alive. She cannot shatter him before she has determined what destructive path Nieman and this Alexis are taking.

She can't wait any longer: she has to go see Nieman.

Half an hour later, Beckett has returned to her car after an abortive interview with the inhospitable doctor. Beckett had barely begun speaking before Nieman interrupted, claiming that Beckett and Castle had destroyed her career with their baseless accusations, forced her to build her practice again far from the virulent grasp of the NYPD. Within two minutes, Nieman had lawyered up and shown—had her assistant show—Beckett the door.

She's seething. She had wanted to wipe that fucking sneer off Nieman's face, smash her head into one of the ten-thousand dollar mirrors that studded her million-dollar office. But she's back on the street and she has to make a different kind of move, right now. Despite her own convictions, she knows that she has to prove that the fraudulent Alexis is just that, a fake. It's the simplest but probably the most painful thing she'll have to do today. Go home, go to Alexis's room, get a hair off a coat or a sweat or a jacket. That's something she can do. That's a start, something concrete.

"Forgot something, Sam, just have to dash upstairs," Kate says as she rushes past the doorman. Her hands are shaking again as she walks toward the loft, and she has trouble unlocking the front door. Her troubles have just begun: she'd hadn't counted on Martha.

"Hello, darling!" her mother-in-law calls out from her perch on a kitchen stool.

"Oh, Martha! Um, you startled me. I thought you were having costume fittings."

"Well, I was, but they finished ahead of schedule. Everything fit like the proverbial Italian handmade leather glove, if you'll forgive my saying so. So, I decided to come home, have some coffee, catch up on a few things. But what brings you here in the middle of the day?"

Fuck, fuck, fuck. She can't go up to Alexis's room. What possible reason could she give for that? Besides, acting is not her strong suit and Martha would see right through her. She needs a sample, she has to have something for DNA. Shit. Wait, she knows. She pivots to the front hall closet. "Maybe I'm coming down with something, but it just seems much colder out and I was nearby and I thought I'd come get a warmer, uh, coat and scarf." Before Martha can respond, Kate has shed her coat, hung it up, found another and rooted in the closet for one of Alexis's. Thank God. A lone, long red hair is clinging to the back of one. Kate slips an evidence bag out of her pocket and puts the hair in. "Got 'em, Martha. Bye!"

Back in the cruiser, Beckett takes out her phone to call Lanie, but she doesn't trust her voice, is pretty sure that she'll lose it the instant she hears her friend's voice. So she texts. "Can you meet me in 10 out by your loading dock?"

A few moments later, Lanie replies. "What? It's freaking winter. Come to my office."

"Can't. Please, Lanie, be there. And don't say anything. Please."

TBC…

A/N Thank you very much for the reviews and follows. It's great to hear from you.