A.N. I do realize Castle's reaction is a bit "cold" to her death, but here's the reason why Also remember what he says is his coping mechanism in the actual series. As always, this is Marlowe's and ABC's swing set; I'm just playing in the park.
Castle locked himself in his office once the detectives left. Being objective and eager to help hid what he was really feeling. He picked up his phone and called his mother.
"Mom…." H started to choke up.
"Darling, what is it?"
"It's Meredith. I came home from a book tour, and…" He repressed some more sobs.
"And what, Kiddo?"
"I found her dead in the loft. Someone killed her. I really need help with Alexis. Please come." He begged.
"Oh, Sweetheart, of course! Besides, your stepfather's been, how shall I say it, a con artist; I need some place to crash until I get on my feet again. "
"Of course. That would be great. The thing is, I can't leave town, so you'll have to fly in."
"But I can't afford….."
"Don't worry, Mother, I'll take care of it; I always do." He said and hung up.
Meanwhile at the 12th
"That does sound like a compelling argument, Detective." Captain Montgomery said. "If Mr. Castle could help us with anything he can think of."
"But, Sir, he's a mystery writer, it's his job to spin some believable story. I know I saw him at the book signing, but still, he could've hired someone to do it for him. I know they've been having some trouble lately, come on, it's the whole celebrity marriage and break up story almost every famous couple goes through, except this one ended in murder."
"Writers pay attention to little details, Kate, he'll be able to pinpoint things we cannot see or possibly know. Celebrities can hide certain aspects of their lives if they really know how to."
"Okay, I'll give him a call, but on one condition; this is a onetime deal."
"You got it."