Shared Obsession Chapter 99

Castle arrives in the bullpen to find Ryan and Esposito high-fiving each other. "You catch a break?"

"We found a motive for taking out our vic," Ryan explains. "He had a rent-controlled apartment, $562 a month, three bedrooms. The law says if he had family living with him and it stays in the family, it stays rent-controlled."

Castle recalls his conversation with Carrie. "Many New Yorkers might regard a deal like that as worth killing for. So what member of his family would inherit the keys to the Castle, so to speak?"

"The vic's daughter," Ryan replies.

"But she's not the one we like for the murder," Esposito adds. "The next-door neighbor could hear arguments between the son-in-law and the vic through the walls. He couldn't make out much, but he got they were about money."

"So are you guys picking up the purveyor of in-law-patricide?" Castle asks.

"Huh?" Esposito responds.

Ryan jumps in. "He works uptown. Unis should have him in here in about an hour."

Castle drops down into his place by Kate's desk. "Tell me we got as lucky as the boys."

"No, and …." Kate's cell phone dings a text alert. "Maybe we did. Lanie says she found some forensic evidence on the body. She wants us to go to her lab."

As Kate and Castle hurry down the hallway in the Medical Examiner's building, they hear Ryan and Esposito's feet pounding the floor behind them. "I thought you texted me," Kate says as she and Castle enter Lanie's domain where she stands at her computer with Perlmutter.

"She texted us," Esposito insists.

"I texted both of you," Lanie declares. "Dr. Perlmutter and I found the same thing on both bodies."

"Orthosilicic acid," Perlmutter announces triumphantly.

"It's a form of silica found in salt water," Lanie explains.

"Oh yeah, and naturally occurring in some organisms. Meredith was into it when she was on one of her supplement kicks. It's supposed to be good for hair and bones. Maybe the victims were both taking it," Castle offers.

Perlmutter rolls his eyes in impatience. "It wasn't in the victims, Castle, it was on them. Both of them came in contact with saltwater – salt water with a very specific composition."

"Your cases could be connected," Lanie speculates.

"The unis should be bringing the son-in-law in around the time we get back to the precinct," Ryan figures. "maybe we'll find out."

"I don't know what I'm doing here," Eric Marx complains. "I didn't have anything to do with my father-in-law's death. I thought it was the local gang. They were pissed off because Frank kept a few of his students from heading in their direction. Christina was always afraid it would get him killed someday, especially the way he loved late-night walks. Her father was too good for his own good."

"Frank Anderson wasn't killed by the gang. They were across town at a gang summit," Ryan explains.

"Your father-in-law was targeted by someone who knew about his walking habits and where to find him," Esposito adds. "Someone with money problems who'd get to keep living cheap in a great apartment."

"Me?" Eric exclaims. "Christina and I were nowhere near Frank when he was killed. We were at my friend Eddie's birthday party from 9:15 until midnight. Then we took a cab home. You can check with Eddie and anyone else who was at the party. And I used a credit card for the cab. I have a receipt."

Ryan throws his pen on his desk as he hangs up his phone. "I talked to Eddie and five other party guests. They all confirmed that Eric and Christina Marx were there."

"And I talked to the cabbie," Esposito reports. "He says the receipt is legit. He remembers Eric and Christina. He thought they were drunk. They were pretty loud in the back seat. But he didn't pay much attention to it. A lot of people he picks up at that time of night are drunk. Still, they were louder than most."

Castle looks over from Beckett's desk. "Like they wanted to be remembered?" he wonders. "They established a solid alibi. Jason Cosway did the same thing by going to that hockey game with his buddies. Could Jason Cosway and the Marxes have hired the same hitman, maybe met him near the same body of water?"

"We checked on The Marxes' finances, Castle," Ryan says. "The neighbor was right. Eric is in a financial hole. If he and Christina hadn't been living with Frank Anderson, they would have been out on the street. No way he could afford a hitman."

"And we found no evidence Jason Cosway paid one either," Kate reminds Castle.

"There has to be some kind of connection," Castle insists. "Wait! The fish tank in Ashley's office. The fish in there were like Nemo."

"The captain of the Nautilus?" Kate asks.

"Wrong movie. Wrong genre. No, Nemo as in Finding Nemo. Alexis was seven when it came out. I took her to see it. Nemo's a clownfish. They live in salt water. Ashley could have gotten the water from the tank on her. Could Anderson's killer have been there too and transferred the orthosilicic acid to Frank's body?"

"I'll ask CSU to get a sample they can check against what Lanie and Perlmutter found," Kate says. "It's a long shot, but it's more than we have now. But they won't have anything until tomorrow. We should all take a break while we can."

"Coming over for what's left of the night?" Castle whispers to Kate. "Work off some frustrations?"

"Castle, we both should really get some rest."

"We can do that too."

Martha's anger vibrates through the door of Castle's bedroom. "How dare you!" He hears a thwack. "How dare you take my dress? You're as thoughtless as your father!" A louder thwack sounds.

Castle bursts into the great room. "What the hell? Mother, have you finally…?"

Kate hurries in, swimming in one of Castle's robes. "What's going on?"

Martha looks up from the couch where she and Alexis are sitting holding scripts. "Have I finally what, Dear?"

Alexis waves a greeting. "Hey, Dad, Detective Beckett."

"You're rehearsing," Castle realizes.

"Yes, I have a callback. So Alexis got up early to run lines with me. Oh! And you believed it! I'm a better actress than I thought."

"It sounded like quite the drama," Castle admits.

"And we had another drama while you were off doing whatever you and Katherine were doing," Martha says.

"Owen?" Castle asks.

"Uh-huh," Alexis confirms.

"I should leave you to talk about it," Kate offers.

"That's all right, Detective Beckett," Alexis tells her. "As a cop, you probably run into more liars than anyone."

"I had run-ins with my share as a teenage girl, too," Kate confides. "So what happened?"

"I was taking my boyfriend Owen out for ice cream at Serendipity to celebrate his birthday. This girl, Thalia, came to our table and told him that she had a crush on him when they were little kids at Camp Chumash together," Alexis explains. "It turns out, she never even went to Camp Chumash, but her friend did. And Thalia wanted to meet Owen. So she staged the whole thing."

"Oh, that is so budding psychopath," Castle comments. "But how did she know you'd be at Serendipity?"

"She could have been following us on social media," Alexis proposes. "And his birthday might have been in some of the articles about how ahead he is in school. She must have put the whole thing together to figure out we'd be there."

"Or someone tipped her off," Kate suggests. "Did you tell anyone while you were in a place where you might have been overheard?"

"My friend Paige and I were talking about it in the Girls' Room," Alexis recalls. "Someone in Thalia's clique might have been in one of the stalls and given her the perfect chance."

"Yeah, the perfect chance," Castle echoes, "to move in for the kill."