A/N: Hello again. This is my first attempt at a Castle story that is more than a collection of one-shots. It begins with a case, but will focus on Castle and Beckett's relationship as well. It's been in the works for a while, but the first installment is now ready.
The usual disclaimers apply to this and all subsequent chapters.
I hope you enjoy it.

Captain Victoria Gates paused at her office door and cast a glance around the bullpen. It was mostly deserted at this late hour, the only ones present being what had become her favorite band of detectives: Katherine Beckett, Javier Esposito and Kevin Ryan. Only a certain wealthy author who'd been of surprising help to them was absent. Beckett was fast asleep at her desk, head pillowed on her arms. Ryan was also snoring away and he looked about ready to topple off his chair. Esposito was the only one awake, and he was at the espresso machine making a cup of coffee. When first assigned to the 12th, she had been surprised to see that particular appliance, until she learned it was a donation to the precinct by none other than Richard Castle.

"Detective Esposito," she called.

"Captain," Javi replied.

"How's it going? The case, I mean."

"It's kicking our ass. We spent all day interviewing potential witnesses, canvassing the area and looking for security and ATM camera footage. We got zilch. CSU reports came back negative, too. Our killer was very careful not to leave any trace behind. I don't get it. Our vic was killed in a busy, very public place, yet not one person noticed? Someone ought to have seen something." He set the coffee cup down on his desk in time to catch Ryan and keep him from falling as he shifted in his sleep. "That was close. I'd never hear the end of it from Jenny if I let anything happen to her brand new husband while in the precinct."

"You've all been going flat out for thirty-six hours, Esposito. Go home, get some rest and start afresh tomorrow, all three of you." She moved to Beckett's desk and shook the younger woman awake. "Kate, wake up and go home."

Beckett came awake with a start. "Uh, yes sir. It's not like we made any progress on the case."

"I can't believe I'm actually saying this, but we should tap every resource, including Castle. Where is he, by the way?"

"Book tour," Kate replied, rubbing her eyes. "In DC. His latest Nikki Heat novel is a raging success. Just like the previous ones."

"When is he expected to be back?"

"Sometime today." Kate's eyes sparkled when she gave Gates the answer.

"You miss him already? He's only been gone a few days."

"It's what he promised to bring me."

"And what might that be?"

"He promised to bring me a signed first edition hardcover copy of Temperance Brennan's latest novel." Now her eyes lit up like a kid's on Christmas Eve. "He knows her personally."

"You seem to have a thing for mystery novels, Detective."

"I'm a fan of the genre."

Gates murmured something that sounded suspiciously like "not just of the genre, from what I see happening here every day", while walking back to her office, but Kate didn't hear it. She was busy gathering her stuff and checking her watch.

"In fact, Castle is already back, but he had a book signing scheduled. I'll call and tell him to come over first thing in the morning, Captain," Beckett called out.

"Very well, Detective. Now, off you go and goodnight."

"Goodnight sir."

-o-

"Is the precinct up for review or something?" Kate asked her partners while they were all in the elevator. "She seemed pretty anxious to have Castle help us on the case."

"She's warmed up to him," Esposito replied.

"He melted Captain Permafrost?" The moment she said that, both Esposito and Ryan shot her curious looks. "His words, not mine," she clarified.

"She saw first hand how helpful he can be, Beckett," Ryan said. "He's worked with us on about twenty cases since she came here."

"Kev's right, Beckett," Espo added. "When you and he were missing and damn near became kitty kibble, do you know what she told that DEA agent?"

"I have a feeling you're about to tell me."

"She told him that two of her people were missing."

"Then she considers Castle part of the team. I had a heart to heart with her while you, Ryan and Castle were making fools of yourselves in Atlantic City, and I made it clear that I always consider Castle to be part of my very good team."

"And tomorrow said very good team is getting back together again," Ryan said optimistically. "By the way, the precinct is not up for review. We're already above the mandated minimum anyway. Gates probably wants Castle around to help close the case quickly. She's had first hand knowledge on how helpful he can be. I think the case with the sniper was the turning point for her."

-o-

"Admit it my dear Detective Beckett, you've missed my sultry voice," Castle answered the phone early in the morning.

"Shut up and come over to the 12th ASAP," Kate growled while trying to put her high heeled boots on.

"We got a case?"

"And, like Esposito said last night, it's kicking our ass."

"I'll be happy to get you out of the fix."

"Don't be so cocky, Castle. There is nothing to go on. No witnesses, no evidence, nada."

"I'm sure I can come up with a good theory or two. See you at the precinct, Detective."

"Don't forget to bring me something edible." She wasn't sure if he heard the last part, but a girl could hope, right?

It took Castle less than twenty minutes, including making a stop for coffee, to arrive at the precinct. He cheerfully greeted the officers at the entrance and made his way to the elevator, holding two paper cups of coffee and a bag filled with donuts, croissants and bear claws.

"Here you go Kate, Grande Skim Latte, two pumps sugar-free vanilla. You also have a choice between donuts, croissants and bear claws."

"Thanks." She took a sip of coffee. "I think I'll have a croissant."

"Help yourself. Also, I'd like to see what you've got so far on the case."

"Sure," she said and bit into her croissant. "Hmmm, nice. Is that chocolate and cream filling?"

"Guys," Castle motioned to the other two as he nodded to Beckett.

"Hey bro, what's up?"

"I'm back. And I brought pastries. Dig in."

"Thanks."

Castle moved to the murder board. "Give me the background."

"The victim is one Ian Lawrence, stockbroker," Esposito replied. "He was found dead two days ago, in a toilet stall at a diner. He drowned after someone gave him a swirlie. The problem is that we have no witnesses, security cam footage or trace evidence to point to the killer."

"A swirlie," Castle repeated. "It's kind of imaginative, I must say. Whoever killed him might have wanted to torture him first."

"Practical joke gone wrong?" Ryan guessed.

"You said he was killed in the restroom of a diner?"

"Yes," Kate said.

"Strange there are no witnesses."

"According to Lanie, time of death was very late at night. The victim had been working late. The place would have had very few customers."

"Still, someone ought to have seen something… Unless…"

"Unless what?"

"Take a look at the crime scene photos. There is an opening window right above the stall. Our killer could have been following the victim, saw him heading for the restrooms, gone to the alley, opened the window, which is big enough for a fully grown man to squeeze through, entered, killed the victim and exited the same way. Have CSU look for evidence on the window and the alley. Also, have uniforms canvass for witnesses and security cameras around the alley."

"It makes sense," Kate said. "It also explains the lack of witnesses. We were looking in the wrong place."

"I'll call CSU," Ryan offered. He reported back to the others a minute later. "They'll be on it. But what Castle said suggests premeditation, which is not what you might expect from a high school prank."

"High school prank!"

Kate, Javier and Kevin exchanged looks. Castle was obviously on to something. He had been on the case for just a few minutes and he was already hot on the trail of something. What it was and how he had figured it out, they didn't know – yet.

"Mr. Castle," Captain Gates said from behind them.

"Captain," Castle greeted her respectfully.

"It's nice to have you back again. I see you're already tackling the case."

"Yes, it's intriguing to say the least." He spotted someone near the break room. "Excuse me," he told Gates. "Ann!"

Officer Ann Hastings walked over to them. "Hello Mr. Castle, how are you doing?"

"I'm fine, thank you. Say, is Paul at work today?"

"He sure is."

"Can you give me his number please? There is something I want to talk to him about."

"Certainly," Ann smiled. She scribbled on a piece of paper and handed it to Castle, who nodded his thanks and turned away for a minute to make a phone call.

"He'll be here shortly," he announced.

"I don't see how Mr. Whittaker can help."

"Call it a hunch, Captain Gates. But something about this case had my spidey senses tingling. It only remains to be seen if it pans out. In the meantime, can I offer you a bear claw?"

"I'd love one. Thank you Mr. Castle."

-o-

Paul Whittaker arrived soon afterwards. "Hey everyone," he said.

"Paul, thank you for coming by on such short notice. Did you bring what I asked for?"

"It's all in here." He patted his briefcase.

"Let's take this to briefing," Castle suggested. They all filed into the briefing room and took seats.

Gates was about to follow them when another detective stopped her. "What are they up to now?"

"That's what I'm going to find out. Mr. Castle's brainstorms sometimes pan out."

"Sometimes? Try all the time, Captain. His craziest, most outlandish theories are mostly to interject a measure of humor, but when he has something good he shares it."

"Let's see what it is this time."

"What are you looking for?" Paul asked.

"I'm not sure… It's just… something about the latest case we've got rang a bell."

"Well, these are all the articles from the Ledger on homicides from the last three weeks."

"Before we start, I'd like to ask you not to reveal anything about what we'll be discussing today. But if I'm right, you'll have a nice little exclusive."

"I'm game."

Paul, Ann, Gates, Kate, Ryan and Esposito watched impatiently as he browsed through the stack of printed pages, all photocopies of articles in the Ledger. After finishing each one he would put it aside and then move to the next one.

"Aha! I knew it wasn't my imagination!"

"Castle?" Kate queried.

"Hold on to your horses Kate. I'm not done yet…" It took another few minutes to double-check his findings before looking up to face his audience. "It was not an isolated incident," he said without preamble.

"Meaning?" Gates asked.

"There are two more murders staged like high school pranks. The first one occurred almost three weeks ago. The second took place exactly eleven days ago, and of course we have our current case."

"What are you suggesting, Castle? Do you mean that the perp is the same for all three murders?"

"If it's not the same killer, then we're talking about amazing coincidences, Espo."

"The staging tipped you off?"

"We'll have to confirm with the precincts investigating the other two homicides, but yes, it was the staging. The first victim was found inside a locker in a closed gym. The second was found under the bleachers of a high school football field."

"I covered that one," Paul said. "The victim was found naked. I didn't include this particular detail in my article, out of respect for the deceased, but the groundskeeper found him frozen under the bleachers in his birthday suit."

"Left naked under the bleachers? Typical high school prank."

"Yeah, except pranks like that take place after spring break, not in the middle of winter," Ryan added.

"Do you think we may be dealing with a serial killer?" Paul asked.

"To be frank, the thought crossed my mind. But in my experience, sometimes crimes with motive are presented as the work of a serial killer. Captain, we'll need to get the files from the other precincts. We should also see if the victims are connected in some capacity."

"I'll see to it. Anything else, Mr. Castle?"

"There is something, but I don't know if you're going to like it."

"And what would that be?"

"Beckett, Ryan, Esposito and I worked a serial killer case once, in collaboration with the FBI."

"You want to call Jordan Shaw?" Kate was a little bit surprised.

"She may be able to help. If similar killings have taken place elsewhere…"

"Castle's right," Esposito interjected. "We should at least look into it."

"You guys just want Shaw and Avery to bring their smart board and the Fed-mobiles again."

"Boys will be boys," Castle said innocently. "But you're right. We shouldn't cry wolf unless we're sure we are indeed dealing with a wolf, or, in this case, a serial killer."

"Get the files from the other precincts, including medical examiner and CSU reports. Mr. Castle, you and Detective Beckett see if you can find any connections between the victims. If not, contact the FBI and ask if there have been any murders with the same MO in the tri-state area."

"If the killings are confined to New York, I'll inform Agent Shaw that we can handle the investigation," Beckett added.

"Keep me informed of your progress and whereabouts. Carry on."

"Yes Captain," they chorused.

"A possible serial killer case," Paul mused. "Works for me."

"Remember to keep your mouth shut. You never heard anything," Ann reminded her boyfriend.

"Play your cards right and the Ledger gets the exclusive, like I said in the beginning."

"I have to go back to the paper. It was nice seeing you all again, guys."

"Likewise, Paul," Castle said. The reporter shook hands with everyone, gave Ann a peck on the lips and left. Gates also left for her office to answer a phone call.

-o-

"According to the information we have on our victim and those we gleaned from the Ledger articles on the others, all three had the following things in common," Castle summarized. "They were about the same age, they were all men, and they were successful both in their personal and their professional lives."

"Go on," Kate encouraged him.

"Now, assuming they were all murdered by the same person, they must have crossed paths with the killer at some point. If I were to do a profile, I'd say the killer is also male, of about the same age as his victims. He probably was an outcast at school, not one of the popular crowd like his victims were. He must have led a normal life until just a few weeks ago, when an event of some sort brought it all upside down and reminded him of a time he'd managed to forget, quite likely after quite an effort and maybe therapy, triggering his rage, which was then channeled into the murders. The three murders were an outlet for the killer's hitherto suppressed rage."

"Or, it could be something more pedestrian," Kate added. "He could have killed the victims for other reasons and staged the crime scenes to throw us off."

"All the above is conjecture, of course. To confirm or reject the theories, we need the case files from the other precincts," Esposito said. "When are we going to have them here?"

"Sometime later today, I guess," she replied. "Depends on how fast Gates can get things moving. So, tell me, how was your book tour? How many chests did you sign?"

"Ha-ha, very funny, Detective. To tell you the truth, it was fine. And I didn't attend any parties. Hence, no opportunities for chest signing arose." Of course, he didn't tell her that hers was the only chest he wanted to sign. It had been for a long time. For the moment he was content to watch her drink her coffee and munch on her croissant while marveling at how quickly he'd provided them with potentially useful clues.

Suddenly, she looked up sharply. "Castle, where is my book?"

"Damn! I had this nagging feeling I'd forgotten something today. Now I know what it was. No need to worry though, it's safe and sound in my place, waiting for you."

"Good to know."

"For what it's worth, I think you should also know that I had to fight for it."

"Castle, you know Dr. Brennan personally. Surely, she and her publicist would have given you the VIP treatment."

"Them yes, her daughter no," he replied. "For a baby, she's a very curious little devil and tends to grab at anything within reach. She kind of reminds me of Alexis, in fact, when she was a baby."

"Really? You had to save the book from her daughter?"

"Yep. By the way, Temperance and I have a lot in common, not the least of which is that we draw inspiration for our books from our partners while solving crimes."

-o-

"Beckett! My office," Gates called. Kate and Castle exchanged looks. Then they got up and hurried to the Captain's office.

"Yes, sir?"

"The couriers with the files from the other precincts will be arriving shortly. Since you're in charge, I expect you to sign for them."

"Yes sir."

"How did the people from the other precincts take it? Did they resent having to send us their case files?"

"If anything, I'd say they were relieved to have someone else deal with the cases, Mr. Castle. They had nothing to follow up on, not a shred of evidence. In fact, your guess about the cases being connected was the first solid lead in any of those murders."

"Three murders to investigate, possibly the work of a serial killer…" Castle mused as they left Gates' office. "We'll need more boards."

"We'll get right on it," Esposito volunteered. "Come on, Ryan."

"In the meantime, I'll familiarize myself with what we've got so far. Okay, let's see… Victim three, if the cases are connected, is Ian Lawrence, 30, works for a financial firm downtown and was killed downtown."

"Yes. A few blocks from the office building where he works," Beckett confirmed.

"Then it's safe to assume that the killer followed him there. Maybe he chose him as a target of opportunity, or maybe he had him under surveillance, learning his habits, his vulnerabilities…"

"You mean he was stalking him."

"Like a hunter would stalk his prey."

"Uh-huh."

"Did Lawrence have any family?"

"His parents are still around and live in Staten Island. He's single, apparently had his share of girlfriends, but claimed to be too young for a steady relationship, although he was hoping for one in the near future."

"Any siblings?"

"Yes, an older brother, who lives and works in San Francisco."

"Could he be our suspect?"

"No, he had no reason to kill his brother. As a matter of fact, they were very close. He even wanted to invest in a venture Ian suggested to him."

"So it's not the brother."

"Yo, Beckett!" Esposito called out. "There's some guy from the 27th for you here. Says he's got the files we're expecting."

"I'll be right over."

"Two down, one to go," Castle said once Kate came back with the package. "Let's see what's in here about Mr.…" He looked at the folder jacket. "William H. Simpson."