"Is that... duct tape?" Castle's tone as he asked the question was astonished, but Beckett thought she detected a hint of admiration in it, too – enough that she gave him a look. You didn't admire a murderer, however unusual their methods. And this was definitely unusual – the victim's entire head was wrapped in duct tape, layers upon layers of it, until it looked like a silver basketball sitting on their shoulders.

Lanie, however, was all business. "That's right. The neighbor found him just like this this morning, when she came in to see why the door was open. I'd say he's been dead since around 10 last night."

"Then what about the blood?" Kate had seen enough crime scenes to know that there wasn't enough of it to be the cause of death, but fresh blood didn't come out of nowhere.

"That would be from the victim's hands." Lanie didn't touch the hands, still bound tightly at the wrist with more duct tape, but she indicated the missing fingertips with one of her own. "Looks like someone didn't want us to know who our victim was."

Beckett frowned at that; it was an unwanted complication in a case that already looked to be difficult. "Was that done postmortem?"

"I'd say so. There's not enough blood for the victim to still have been alive. As for the face, that will have to wait until we can get all this tape off."

"All right. Call us when you're ready." Beckett looked away from the body, gaze searching the crowd of police until she located Ryan and Esposito. "You two start knocking on doors. Castle and I will see if there's any security camera footage."

The building didn't have cameras on each floor, but it did have cameras in the lobby. An hour later, she and Castle were in the precinct, watching the tape from the time of the murder, carefully pausing to take note of each face. Later they could be matched with known residents of the building. This wouldn't help if the murderer were also a resident, of course, but it was a place to start.

"Look at that guy." Castle pointed to the screen, where a man in a polo shirt and slacks hesitated, glancing around with a somewhat confused expression. "Looks like he doesn't know where he's going."

Kate nodded slowly. "But this didn't look like a random crime or a robbery gone wrong. There was no sign of forced entry and nothing appeared to be missing. He might be lost, but he's probably not our guy."

She thought no more of him until they were called down to the morgue to watch Lanie cut the tape from the victim's face. Lanie had already removed as many of the outer layers as she could, laying them aside to be checked for fingerprints. The final layer, however, had to be cut, to avoid damaging the skin beneath.

"Can I do it?" Castle asked, clearly excited by the prospect.

"No." Kate and Lanie replied in unison, then glanced at each other.

"Ready?" Lanie picked up the shears and held them poised above the tape, thin enough now that the outline of features could be seen.

"Go ahead."

Slowly, cautiously, she began to cut. When she was done, Lanie carefully pulled the tape apart to reveal the face beneath: a face that showed clear signs of asphixiation and was also unexpectedly familiar.

"If the lost guy is our victim, maybe it wasn't the resident in that apartment who was killed," Castle suggested, after a moment where they both stared in stunned silence.

"You've seen this man before?" Lanie looked between them, eyebrows arched.

"We saw him on the surveillance tape," Beckett explained as she dug her phone out of her pocket.

"Where he didn't act like a resident," Castle added.

"I'll call Ryan. They should know who lives in that apartment by now."

Back at the precinct, they all stared at the driver's license photo of the apartment resident. "That's the same man," Beckett said at last, voicing what they were all thinking.

"Or maybe it's not," Castle offered. "Maybe he has a twin."

"A twin?" Esposito gave him a disappointed look. "It's like you're not even trying. That actually almost makes sense."

"Or maybe," Castle replied, grinning as he rose to the implicit challenge, "it is the same man – at least his body. But there's something else inside."

"Like that movie -" Ryan started to join in, when Kate interrupted him.

"Body snatchers? Really?" She was used to it by now and, if she were honest with herself, she might even miss Castle's bizarre solutions to cases if he ever stopped offering them. Which didn't mean she'd admit it, nor that she'd encourage him.

"Let's find out what we can about our victim. We need to know when he got home and where he was coming from. And let's check his birth records – let's see if there's a twin we don't know about."

They didn't find a record of a twin, but they did discover that their victim, Jerome Whitmire, was a physician. While his credit card and phone records were being run, Castle and Beckett went down to the practice he shared with several other doctors.

"We don't take walk-ins," the heavyset nurse behind the desk stated firmly, only the graying top of her head visible from their vantage point as she looked at the paperwork in front of her instead of at them.

"We're not here to see a doctor," Beckett stated firmly, producing her badge and holding it up, waiting for the nurse to look up and see it. "We'd like to talk to you about Dr. Whitmire."

That got her attention; she looked up swiftly, her expression concerned. "Has something happened? I thought it was strange when he didn't come in today."

"But you didn't report it?"

"Well, he'd been taking more time off lately," she offered, though it was obvious she was uncomfortable explaining. "I thought maybe he'd just forgotten to call this time."

"More time off?" Castle asked and she was used enough to his joining in the questioning that Beckett took his contribution in stride. There was a time when she'd thought she'd never get used to it. Funny how it had changed. "Did he say why?"

"Something about family. It sounded like maybe someone was sick?"

"Did he say who?"

"No." The nurse shook her head, glancing between Castle and Beckett as if she wasn't sure which one to look at. In the end, she settled on Beckett and looked directly at her as she continued. "But Dr. Whitmire wasn't the friendliest type. He didn't encourage asking personal questions. Don't get me wrong – he was a good man to work for. But he liked to stay professional."

Beckett nodded and changed the subject. "Do you know what time he left last night?"

"Let's see." The nurse checked the computer in front of her. "He saw his last patient at 5:15. His notes on that patient were submitted an hour later. He probably left right after that."

"But you can't say for sure?"

"No, I'd already gone home by then. I usually leave once the doctors are done seeing patients."

"Is there anyone who would still have been here?"

"Not that I know of. The doctors take turns closing up. Yesterday was Dr. Whitmire's turn."

"You mentioned he'd been having some sort of family troubles. Had he been acting differently as well? Worried or tense, maybe?"

"No. Now that you mention it, it's strange. He seemed... relaxed. Maybe even happier." She paused to think, then brightened. "If you want to know more, you should ask his fiancee."

By the time they'd returned to the precinct, techs had gone over the surveillance tapes more thoroughly and found what appeared to be their man arriving, albeit three hours earlier than the instance they'd seen previously.

Before trying to find Whitmire's fiancee, Castle and Beckett watched the section of tape that had been indicated.

"He looks just the same," Castle marveled.

"But he acts completely differently. Look at the way he's walking – he's done this hundreds of times before."

"Pod people. I'm telling you, that has to be it."

Kate just shook her head. "Let's see if we can run his face through the DMV database. He doesn't have a twin, but maybe there's a lookalike."

"That's it! It's not a twin – that's him, but from a mirror universe! That's why he cut off the fingers: to hide that their fingerprints are the same!"

"And why would he kill another version of himself?"

"Maybe he wants to take his place." Castle eyed the video and looked thoughtful. "But he must have shaved off his goatee."

"A goatee. Right." Beckett smirked. "I'll tell them to check it out. Meanwhile, let's find this fiancee."

Whitmire's fiancee was a pretty girl in her mid-twenties named Rachel Rodriguez. She was a graduate student with no arrest record and she looked entirely intimidated to be visited by the police.

"I'm sorry for the mess," she said, carefully shuffling books and papers from the couch onto the kitchen table. "I live alone and I don't always have time to clean up."

"That's fine." Beckett gave the girl her best reassuring smile. "You should sit down."

Rachel hesitated, then turned a kitchen chair around and perched on the very edge of it, leaving the freshly cleaned off couch for Castle and Becket. Her hands twisted together in her lap and her eyes were wide and anxious, but that didn't necessarily indicate guilt. Most people were nervous under these circumstances and why wouldn't they be? The police weren't in the business of bringing good news.

"We're here about your fiance," Beckett began.

"Jerry? Has something happened?"

"He's been murdered."

"What?" Ms. Rodriguez' brown eyes widened even more, something Beckett wouldn't have believed possible if she hadn't seen it, and she moved her hands to grip the seat of her chair, leaning forward intently. "How did this happen?"

Ignoring her question, Beckett maintained her distance and proceeded to ask the usual questions. "When was the last time you saw him?"

"Oh... it must have been three weeks ago? Maybe a little longer."

"Why so long?" Castle glanced around the tiny apartment, then back at the girl. "Isn't it strange not to see your fiance for that long?"

Rodriguez looked desperately unhappy and fumbled around in yet another pile of papers before she came up with a box of tissues. "But we weren't. Not anymore. He broke it off."

"When?"

"About a month ago." She sniffled miserably into a tissue. "He wouldn't tell me why."

"And you hadn't seen him since?" When she'd been a new cop, Kate would have found it hard to press someone crying like this, but now, she didn't hesitate. If this girl really had cared about their victim, she'd be better served by answering questions so they could find the one who'd did this than by tea and sympathy.

"He wouldn't return my calls," Rodriguez said. "So I stopped trying after a week." For the first time, she showed a hint of backbone. "I wasn't going to beg."

"His nurse said he'd been having family troubles," Castle put in. "Do you know anything about that?"

"I don't know. I think..." she frowned, forehead wrinkling as she tried to remember. "I think he said something about his brother."

"His brother?" Castle asked eagerly, giving Beckett a significant glance that she carefully avoided.

"I think he was sick. Cancer, maybe?"

"There's no record that he had a brother."

"That's what I said! I said he didn't have a brother, but he said I was wrong."

Beckett ran a hand through her hair and stared at the murder board, sighing in frustration. "No matter where we look, there's no evidence he ever had a brother. So who was he talking about?"

"Maybe a fraternity brother?" Ryan suggested, though he didn't sound confident in the idea.

Castle opened his mouth to say something, but before he could, a voice called across the room. "Beckett? Someone here to see you."

Curious, they all turned their heads, only to freeze as their victim walked toward them, looking puzzled. "I'm sorry, but I came down here because there must be some mistake. My nurse told me you'd said I was dead?"

The three detectives and Castle exchanged glances. "You're Jerome Whitmire?" Beckett asked.

"That's right. As you can see, I'm very much alive."

"Then who's the man who was found dead in your apartment?"

"In my..." Whitmire, or whoever he was, turned pale. "And he... looked like me? Oh no. Andrew... it must be Andrew."

"Who's Andrew?" They all asked it, not in unison but near enough.

"My brother. He's my twin brother."

Under the circumstances, no one was quite sure how to treat the man claiming he was Whitmire. Was he a bereaved relative or a suspect? In the end, they treated him as a relative, seating him in the room they kept for victim's family, but Beckett's questions were harsher than they usually were for those who were brought there.

The questions might have been harsh, but he answered them willingly. No, he couldn't explain why there was no record of him ever having a twin. Yes, Andrew was sick.

"He had pancreatic cancer," Whitmire said, blinking rapidly to hold back tears. "He was terminal. That's why I allowed him to stay at my apartment."

"Then where were you yesterday, Dr. Whitmire? You had a sick brother at home and patients to see at work. Why did you just disappear?"

"I was unconscious. I hit my head and I was unconscious in the hospital all yesterday." He looked up to meet two extremely skeptical faces. "I know it sounds strange, but the hospital should have a record of it."

And the trouble was that the hospital in question did have a record of it.

"It all checks out." Beckett hung up her phone and looked up at the others. "Our corpse has terminal pancreatic cancer. And all evidence suggests that the man who came in today is, in fact, Jerome Whitmire."

"But if our vic is Andrew Whitmire, why is there no record of him being born?" Esposito eyed the murder board and asked what they were all thinking. "He has a driver's license and employment records, but it's like he came out of nowhere."

"And why," Castle added, "would anyone want to kill him?"

"Let's find out. Ryan, you and Esposito go check out his former workplace. Castle and I are going to verify Whitmire's story in person."

The emergency room was crowded and they had to wait behind an elderly man who seemed confused by the instructions of the harried woman at the reception desk. Beckett could have pushed past him, but she was polite. She waited.

When it was their turn, once again, they were treated to someone who didn't even glance in their direction. Instead, she shoved a clipboard with paperwork and a pen in their direction. "Fill this out and be sure to have your insurance information if you have any."

"That won't be necessary." Kate was calm but firm as she showed her badge, then handed over their printed copy of the record of Whitmire's hospital stay. "We'd like to ask some questions about this patient's stay."

"Sorry about that. It gets hectic in here on a Friday night." The receptionist took the record and glanced at it. "It says he came in by ambulance. You should talk to the ambulance driver."

"Is he working tonight?"

"Let me look." Now that she knew they weren't here to actually use the ER, the receptionist was far more helpful than she'd been to the man she'd dealt with previously. "Looks like he's off tonight, but I can give you his number."

"Thank you. That would be appreciated."

"I don't know what I can tell you." The EMT who'd been in the ambulance, one Ambrose Dunban, was sullen, most likely annoyed at being interrupted on his night out. "We got the call and went to check it out. The door was open and he was face-down on the floor, out like a light."

"What time was this?"

"About 11:30 – no, maybe closer to midnight."

Beckett mentally raised an eyebrow. At that time, their victim should have already been dead. "And you picked him up at this apartment?"

"That's right."

"And you didn't see anything else. Nothing out of place?"

"No, but I wasn't really looking. Once I saw it was Jerry, I just wanted to make sure he'd be ok."

"So you knew the victim."

"Sure. He worked at the hospital sometimes. He was a good guy."

Castle had remained surprisingly silent so far, but he spoke up now. "You said you 'got the call'. What did you mean?"

"911 call. Said someone was unconscious at that address."

Beckett stared at him, feeling that thrill she always got when she knew she had them. "There was no 911 call."

"Sure there was."

"No, there wasn't." She didn't even have to check; she was certain of it. A 911 call would have summoned police and they would have found the body in the bedroom.

"Look, all I know is that I got a call that said it was from the dispatcher. If it wasn't, how was I to know that?"

"Did you recognize the voice?"

Dunban shook his head.

"Was it a man or a woman who called?"

He paused to think before he answered. "A man."

On the way back to the precinct, Lanie called to put the final nail in the coffin. One of the Whitmires had cancer all right, but it wasn't Andrew.

Faced with their evidence, Andrew crumbled - but only in part. He admitted to the murder, but despite everything, he continued to insist he was Jerome, insisting even as he was led off in handcuffs.

"I guess he wanted his brother's life so badly, he'll take it even if he has to go to jail," Esposito offered, staring after the man with an expression that made it clear he didn't begin to understand. But then none of them did. Without his brother's career, what made his identity so important to cling to?

"I don't know. I think I get it," Castle said, still staring where Andrew had been, even though he was no longer in sight. "If he doesn't at least keep the name, he killed his brother for nothing."

"The one thing I still don't get is why there was no evidence of Jerome having a twin. Where's Andrew's birth certificate? People just don't appear from nowhere." Kate shook her head and turned away, back to the half-completed report on her desk. She didn't like unanswered questions and this one was going to bother her.

"I told you: he's not a twin. He's evil Jerome, from a mirror universe."

"Right." Kate rolled her eyes as Castle reached across her to pick something up from her desk.

"Look, I was right! Here, on his driver's license: he had a goatee!"

Beckett looked at the printout of Andrew Whitmire's license, then back at Castle, and slowly smiled. "All right, Castle, you win this time. You're right. Jerome Whitmire was killed by his mirror universe self."

"Yes! I knew I'd be right one of these days!" Grinning, he pumped his fist in the air, completely unembarrassed by the stares of the remaining detectives. It was childish and ridiculous in a man of his age and yet when it was him, it was endearing.

Ryan gave him a high-five, but Esposito just shook his head and looked at Beckett. "You sure you want to encourage him like that?"

"I'm sure." Kate got to her feet and picked up her coat from the back of her chair. "Come on, hot shot. Let's take that celebration elsewhere."