So folks this is the last chapter. I hope that I tied up all the loose ends for you and that you enjoyed reading it as much as I enjoyed writing it. Kett, I hope it was as good as you hoped. I hope it's a birthday present that you will enjoy again. Thanks everyone for following it and for the reviews. This is my first completed story, so I hope it was an ending fitting for Castle.

Chapter Eight

Kate pushed open the door and walked into an empty room. It looked as though no one had been there for months. There was no furniture or even light fixtures on the ceiling. It was completely empty.

"You have GOT to be kidding me!" Exclaimed Beckett. "We finally get a lead onto where he was going and we hit another dead end."

Riing Riiinnngg

"It's Ryan. What's up Ryan?" Beckett asked through the phone. "Tony Lopiccolo. You don't say. Look into it more will you. Financials if there are any. Known acquaintances. Anything. Thanks Ryan." Beckett hung up her phone and looked at Castle and Javi who were still taking in the eeriness of this empty apartment. "Ryan said that the phone device that was found was purchased two days before the murder by Tony Lopiccolo. Paid for it with a prepaid Visa card. Tech is trying to figure out where the calls were routed to. As for now… wait." She said as she walked over to the seemingly blank wall. "Espo you got your blacklight on you?" She asked holding out her hand waiting for it. Esposito handed her his mini blacklight that he always carried with him just in case. She turned it on and scanned the wall. Under it's rays the writing appeared.

"Wow…would you look at that!" Castle exclaimed stunned. "It's like a chemistry lab whiteboard. Look at all those chemical compounds. I'm starting to wish I had paid more attention in chem class." He said as he jotted down the formula that was written on the wall.

"Hey guys." Espo yelled from across the room. "Look at this." He was standing in the corner looking down. From where Castle and Beckett originally were it didn't seem that anything was there. They got closer and found what looked like a mutilated pen on the ground. Espo put on a pair of gloves and picked it up for a closer look. "There are wires in here. It's like a hidden remote device or something." He said as he looked it over.

"Wait a second." Castle said as he pulled out his phone. "Yeah that's exactly the same pen that was on the body when they brought it to the morgue. Look." Castle showed Beckett a picture from his phone.

"You're still taking photos of things you shouldn't be Castle?" Beckett snipped.

"Well, it's easier to remember the little things that way. Anyway you're focusing on the wrong part here. It's identical. Maybe the pen in the morgue was some kind of remote control device as well." Castle explained quickly to get the focus off of what he did wrong.

Kate rolled her eyes at him before giving him a little smirk. She took her phone back out of her pocket and called Lanie.

"Hey Lanie, I know this isn't in your job description but could you do me a favor?" She asked as she awaited the reply. "Thanks, could you look more closely at Aaron Summers personal effects that were brought in with him. There should be what looks like an expensive ink pen….yeah that's the one…could you try writing with it? I know it's a weird request just humor me please Lan. Lit up? Can't write with it, but it lit up when you clicked it. Ok. Thanks girl." Beckett said before she addressed the men in her company. "So Lanie is going to have that pen sent to the precinct for me. It seems that you were right Rick. It's not just a pen. Now we have a new mystery to figure out. What does that remote go to."

"Hey does that vent seem off to you?" Espo asked as they were getting ready to leave. He walked over to the vent at the bottom of the wall. It was a little lopsided and he was lucky to have noticed it. He took the vent off and found a note book jammed in the back. As he paged through it his face changed from confusion to understanding. "Do you guys know what this is?" He asked

"No you are still holding it Javi. Since you seem so giddy about it just fill us in." Kate joked.

"Those compounds on the wall. It was what he had been working on in the military. According to these notes he developed a dna specified weapon. The chemicals in this weapon would only be deadly to the person it was designed for. The weapon didn't work without someone's dna." He said as he looked up at two slightly confused faces. "Lets say I developed a bullet from this compound, and my intended target was Castle. In order for this bullet to do him deadly damage I would need his dna worked into the chemical compound of the bullet. Otherwise, it might leave a small hole, but it wouldn't penetrate far enough in to do any damage and the chemicals wouldn't spread they would just stay solid. This is why he had the break down. It was a genius idea in theory he just couldn't justify keeping the program going to develop it. I mean how are you going to get dna from every target to make this a weapon that will do it's job. It looks like he was testing the chemical compound mixed with his own blood. The last entry was from the day of the murder. He has it marked down as a 75% success rate."

"So what…someone found out he was still working on this project and used it against him? I mean that would explain why were couldn't find a trace of the bullet. Let's get back to the precinct and see what Ryan found on Tony Lopiccolo a.k.a Aaron Summers. By the time we get back the pen should be waiting as well." Kate said as they walked out of Tony Lopiccolo's empty apartment.

A half hour later they were back at the precinct. They had just stepped out of the elevator when Ryan came up to them.

"Hey guys, I found a lot while you were gone." Ryan said as the group walked towards their respective desks. "Tony Lopiccolo not only used that Visa to purchase the router, but he also purchased two tickets to Switzerland for the night of the murder. Red eye. One for him and one for a woman named Susan Franklin. I couldn't find anything on her. No driver's license, accounts nothing. I found one bank account under the name Lopiccolo with a balance of $43,000. I'm thinking Tony was Aaron." Ryan stated triumphantly. "Why don't you guys look more surprised by that?" He asked unsure of himself now.

"Because we know that Tony Lopiccolo and Aaron Summers are the same person. He was renting an apartment under that name. Sorry, Ryan it was a great deduction though. So we have a mystery girl now too though. Anything else?" Kate asked

"Yeah, tech was able to find out where those calls were routed to. I got the number right here I was waiting for you guys." Ryan stated as he pushed the speaker button on the phone and dialed.

"911 what is your emergency?" came a voice from the other side.

"Um hello." Said Castle since no one else was responding.

"A murder? Where are you located?" asked the voice.

"I didn't say anything about…" Castle started.

"The college huh…are you at the murder mystery dinner?" asked the voice annoyed.

"Well…" Castle started again.

"Look I don't have time for pranks right now. It's part of the show the guy dies …hence the murder in murder mystery. Stop calling." The voice said again before disconnecting.

"A recorded message?" Beckett asked more to herself than the others. "Ryan see who that number is registered too."

"Just got an email about it….wait….what?" Ryan said as he turned his screen for her to see.

"Tony Lopiccolo?" Beckett asked amazed. "This wasn't a murder Castle it was a suicide."

"That would mean that the remote pen must operate something at the theater. Shall we?" Castle asked as he picked up the evidence bag that was sitting on Beckett's desk.

When they got to the theater it was empty. There were flowers and wreaths lining the outer walls of the building. A lot of people wanted to show their love and loss of Aaron Summers. Beckett and Castle walked up onto the stage and looked around. Castle walked to the spot where Aaron Summers took his last breath and spun around clicking the remote pen.

"Stop Castle." Beckett ordered as she stood off stage. "Click it again right where you are."

She heard something from inside one of the pillars next to her. She rubbed her palm up and down the back when she found a section of the wood that had been cut. She reached into her pocket for her pocket knife. Using it as a lever she managed to get the piece out revealing not only a gun positioned directly where Castle was standing, but a dvd with Meredith written on it. "He really did it himself Castle. He rigged the gun to go off when he clicked the pen, which was probably in his pocket. He had done that scene a million times so he knew everyone's blocking. He made sure they were standing out of the way so the bullet had a clear shot." She said as Castle made his way over to her. She put on her gloves and pulled out the gun and put it in a baggie, she also took the dvd out and handed it to Castle. "I'm going to guess this is his note. Let's get back to the station. I will have the boys bring in Meredith."

When they got back to the precinct they saw Meredith Black pacing in the conference room. Beckett decided she needed to fill her Captain in first, so she knocked on Gates door. She told her about the router and the alias. She let her know that they found a dvd with Meredith's name on it and asked if she would like to sit in while they showed it to her. They went into the conference room as a team. It was just the way they did things. Seeing that many people walk in together made Meredith's heart sink.

"You found something big didn't you? You all look sympathetic and it's freaking me out a little." Meredith said with a nervous laugh.

"Meredith…" Beckett began. She looked at Castle who gave her a reassuring nod. "Meredith we found out what happened to Aaron. I am so sorry, but it seems that it wasn't a murder, but a suicide. He set up a gun at the theater that was controlled by a remote pen he had kept in this pocket. He used a bullet that he had designed while in the military. We also found this." Beckett handed her the dvd. "If you'd like we can sit and watch it with you."

"I would appreciate that Detective." Meredith said as she sat down trying to process the information she had just been given.

Beckett walked over to the tv, and put in the dvd. She hit play and Aaron Summers filled the screen.

"My dear Meredith. If you are watching this then it seems I have failed you. I assume you know what I was also to be wed to Madeline McKenna. You have to believe me when I tell you that I didn't want to marry her. I wanted to be with you. I was forced into this Meredith. Seamus McKenna had gotten his hands on my medical records from the military and was threatening to go public with them. He needed me to marry his daughter so she could get her green card. He paid me $50,000 to do it and promised to keep the records sealed as long as I kept my end of the agreement. I thought I was being smart. I thought I had it all worked out. I used some of that money to set up different identities for us. I had planned to whisk you away to Switzerland where he could never find us. I had reconstructed my weapon formula. I thought I had it figured to where it would give the illusion I was dead. Stop my heart for a few minutes. Long enough for everyone to think I was gone, but not long enough to where I couldn't get away. I was going to send you a text telling you to pack a bag and meet me at the airport no questions asked. It had a 75% success rate just slowing down my blood in the lab. I'm so sorry my love. I never meant to leave you permanently. I never meant you any pain. Please Meredith, please forgive me. Know that I loved you and only you. I'm so sorry."

With that the screen went blank. Meredith sat weeping on the couch for about ten minutes before she stood up and walked over to Beckett. She held out her hand to shake Beckett's.

"Thank you Detective. I know what happened now and hopefully I can move on." Meredith said.

"I'm going to go after McKenna for extortion and bribery Meredith. It might not be much but he is responsible for putting that kind of pressure on Aaron. At least he can get some justice." Beckett stated.

"Thank you Detective." Meredith walked out.

"Mystery solved it seems Detective. I must admit that was an ending I didn't see coming." Castle said as he walked with Beckett to her desk.

"Me either, but those are the endings that make this job worth it. Someone else may have never figured out the puzzle. Meredith may have never gotten to say goodbye the way she did in there." Beckett said. "Just promise me one thing Rick. If you ever get blackmailed that way, and seriously think your only way out is to pull something like that. Tell me…let me help you."

"Always, Detective. Always."