In the interrogation room, Beckett asks castle about the time he stole a police horse ("Borrowed") while he was naked ("It was spring"). Charges were never filed, and we'll see why later. He offers to let her spank him, but she asks about Alison Tisdale, deceased. He says he doesn't know her, although they may have met at an event. Then she hits him with a picture of Marvin Fisk, a small claims lawyer strangled two weeks ago. Again, Castle says no, but manages to make it a double entendre, somehow. Then Beckett brings out the crime scene photos. Castle instantly recognizes a scene from Flowers for your Grave, and Fisk's pentagram-festooned crime scene was apparently from Hell Hath No Fury, according to Beckett. Castle calls her a "hardcore Castle groupie" for knowing the latter book, and she stammers when asking about his fan mail. He is familiar with psychopathic methodologies, so he gets her drift, then compliments her eyes. He asks for copies of the photos to show his writer buddies -- Patterson, Cannell -- because having a copycat is apparently a badge of honor. She gives him the stinkeye and leaves.
Castle returns home to his loft at 12:45 am and finds his mother dancing and singing to "I'm Just a Girl Who Can't Say No," being played by her latest gray-haired love interest. She apparently used to sing and dance at the Palace; Castle asks the old dude if he was aware it was Martha's theme song. Removing her headphones, the studious Alexis asks if he was made someone's bitch in prison, and Castle offers her "baby bird," which is apparently when he sprays whipped cream into her mouth like a momma bird regurgitates into her babies' throats. She declines, having brushed, so Castle helps himself. She asks if he was arrested, vowing to check out a fansite, but he reminds her to stay off the fansites, and tells her they want his help. He calls the murders senseless, in that they make no sense -- the books are two of his "lesser works," so why would a fan choose them to emulate? He pulls the books off of one of his many shelves of Castle books to ponder. Someday, I hope to have at least half a shelf full of books I've written, so I can just pull one down for reference, or to sign and give to visiting guests. That would be awesome.
Cut to Beckett bringing a box of Castle hardcovers to the other detectives, tells them to find the connection between the victims. These books are all from her personal library, according to the bookplates. (Awww...) The guys tease her for being a fan. "...Of the genre" she says. "Then why are you blushing?" one of them asks. One detective can't believe she reads this stuff in her spare time, since crime stories are the last thing he wants to read about when he gets home. She says she's curious how people can do stuff like "this," and holds up the flower crime scene photo. The answer -- and possibly the next victim -- are in these books, she says. ...Not the next victim's name and occupation, of course, but I guess reading them couldn't hurt? Unless it took time away from following leads? Promising leads that maybe won't get followed up until the very end of the episode?