Beckett is hanging on for her life as she clutches the outer edge of a tall building. Her fingers are slipping. If she falls, she's dead. A voice is heard in the distance. Beckett calls for Castle. Will he get there in time? We'll have to wait to find out as we jump back three days to see how she got here.
Alexis is having a hard time writing her valedictorian speech. As for Castle, he'll have the house to himself after the graduation ceremony. He plans to do a John Woo double feature. Beckett happens to be a fan of the acclaimed action director, so she gladly accepts her partner's invitation to join him for a movie date. First things first though. Yes, there's another one of those pesky murders that needs solving.
Orlando Costas is found dead in alley. He was shot in the shoulder with one gun, but the kill shot was done execution-style with another. The victim used to be part of a street gang, but he cleaned up his active to serve honorably in the military. Orlando's girlfriend, Marisol, says he'd been under financial pressure lately. The victim broke into a house before he was killed. That's where he was shot in the shoulder. He stole files belonging to someone the team knew very well: Captain Roy Montgomery.
The new twist in the case leads everyone to believe that the mystery surrounding Beckett's mom's murder is about to be revisited. Castle knows that his partner will be in grave danger if she starts digging again. He assures Beckett that he's there for her as they briefly hold hands. As for the case, the victim called a member of his old gang before he was murdered, but this guy didn't do the killing. In fact, DNA found under the victim's fingernails match DNA found at another crime scene. The team realizes that the man who killed Orlando Costas is the same person who shot Kate Beckett.
Beckett wants to keep this investigation between the immediate team only. Ryan doesn't feel right about this. Castle isn't thrilled either, especially after getting a call from the mystery man who warned him to keep Beckett away from her mom's case. As for the current case, Beckett learns that Orlando was hired by someone from his military days. Someone dangerous. They met at a church where surveillance footage provides an image of the man the team seeks.
Esposito sees that the suspect was holding a keychain from a rental company. Beckett wants to follow this lead, but Castle wants her to stop. He tells her why. Castle spills the news about how Montgomery's friend struck a deal to keep Beckett safe. He's been trying to keep her safe, too. Beckett is angry that Castle kept this from her. She wants to know how he could do this. It's because he loves her. This is something she's known for about a year.
Castle finally lets out all the things he's been holding back for so long. He says, "Four years I've been right here. Four years just waiting for you to just open your eyes to see that I'm right here. And that I'm more than a partner. Every morning I bring you a cup of coffee just so I can see a smile on your face because I think you are the most remarkable, maddening, challenging, frustrating person I've ever met. And I love you, Kate, and if that means anything to you, if you care about me at all, just don't do this."
Castle's heartfelt speech doesn't stop Beckett from wanting to go after the people who shot her. That's not something he can watch happen. Castle tells Beckett it's over. He's done. As for the case, the now-undermanned team learns that the shooter is going by the name Cole Maddox. They track his car to a location. Ryan's desire to assemble backup is quashed as Beckett and Esposito head to the scene. He dials Castle's number, but the call goes unanswered.
Beckett and Esposito find a room containing Montgomery's files. Maddox gets the drop on them. He knocks Esposito unconscious. Beckett gives chase. She engages in a violent confrontation with Maddox on a rooftop, but ultimately loses the battle. That's how she ends up hanging over the side of a building. Beckett cries out for Castle. Finally, a hand pulls her up to safety. It's not Castle though. It's Ryan. He brought backup, including a very angry Captain Gates.
Gates lets Beckett and Esposito know they are on administrative leave effective immediately. They both hand over their badge and gun. Beckett tells Gates to keep hers. She resigns. As for Esposito, it doesn't look like he's going to be forgiving Ryan anytime soon. All this happens as Alexis gives her valedictorian speech. It's about moving on. It's about the people who will be with us no matter what. She says, "They are our solid ground. They are our North Star. And the small, clear voices in our hearts that will be with us always."
Later that night, there's a knock on Castle's door. Beckett is on the other side. He wants to know what she wants. She finally tells him what's in her heart. She says that what she wants is him. Beckett says she's sorry. She says the killer got away and she didn't care. She almost died and all she could think about was him. This is the moment we've all been waiting for. Castle and Beckett finally, finally, finally give in to their passion.
As we mentioned, Maddox got away. He makes his way over to home of the mystery man who has been contacting Castle for the past year. He's identified as Mr. Smith. Maddox wants the sensitive information Smith holds about his employer. He assures Captain Montgomery's friend that after he gets it, he's going to put Kate Beckett in the ground once and for all.