Castle/Recap/S4 E23 Always

An ex-burglar turned soldier is found murdered in an alleyway, having apparently been forced into taking one more job -- which transpires to be breaking into Captain Roy Montgomery's former home and stealing his files. Beckett is immediately placed on edge, suspecting that it revolves around her mother's cases, suspicions which are confirmed when DNA found on the scene matches DNA found at the scene of her shooting a year before.

Faced with the prospect of locating the man who shot her and finally uncovering answers to the questions she seeks about her mother's death, Beckett begins to spiral back down into obsession again, which prompts a crisis on Castle's part as he must face the decision of informing her of the secret he's been keeping and risk losing her forever, or watch her get destroyed by the conspiracy she chases. His choice will in turn will force Beckett to confront what she truly wants...

Tropes:

 * Anguished Declaration of Love: Twice:
 * Castle gives another one of these to Beckett as part of a desperate attempt to both (a) justify his keeping secret the contact who was protecting her with Montgomery's files and (b) persuade her to drop the investigation.
 * At the end
 * Arc Words: "Always".
 * Big Damn Heroes: Ryan for Beckett, but she hallucinates that it's Castle coming to save her, which is one of the things that helps prompt an epiphany.
 * Bittersweet Ending:
 * : And how.
 * Breaking the Fellowship: Played with.
 * Call Back:
 * Epiphany Comeback: Played with -- Beckett gets her ass kicked by the man who shot her and experiences an epiphany as she's dangling off the side of a building...
 * Holding Hands: Twice. Once early in the episode as a gesture of solidarity
 * Mood Whiplash: The ending.
 * Not So Different: A subtle example; in this episode Beckett, Ryan and Esposito break the rules to bring justice to someone they deem deserving... which is not a million miles away from the actions of the three cops who started the dominoes that ended with Johanna Beckett's murder.
 * Official Couple: As of this episode,
 * Special Edition Title: As with other significant arc episodes in the series, the title card is shaded a different colour from the usual brown (this time green) and features no music.
 * Turn in Your Badge: Played straight; Gates practically recites this trope word for word to
 * Wham! Episode: And how. Seriously.
 * You Called Me "X" - It Must Be Serious: Castle towards Beckett, of course, but Ryan and Esposito get in on the act when Ryan confronts Esposito with his misgivings about their entire operation.
 * Wham! Line:
 * Wham! Line: