We start off with a young, attractive blonde being stalked and ultimately killed.  When Beckett, Castle and Laney show up at the crime scene, they notice that she has been strangled and placed in a restful position with her arms across her chest.  Castle is instantly reminded of a case from 4 years ago…the Triple Killer!

C&B are quick to dismiss but when they are back at the lab and Laney confirms that the rope used to strangle our victim, was the same rope that 3XK used in his killings.   3XK has returned!!!!  

Once it’s determined it is 3XK, Montgomery calls a meeting of all the cops in the precinct and they go through the history of 3XK…always kills in 3s, young, pretty blondes in their apartments, and usually as a cable man or repair man of some sort.  That’s what makes this case a little more interesting…it’s sightly different due to the fact that victim #1 was killed in an alley.

Ryan finds out there was a guy at victim #1’s work who was creeping her out named Paul, otherwise known as creepy sweaty dude.  They interview creepy sweaty dude and he confesses that he liked the vic but never touched her.   He also happens to be a security guard.  

Montgomery comes over and tells C&B that they have another victim.  Kim is the next victim and killed in her apartment just like the original 3XK victims.  They search the apartment and find a name tag in the couch “Vince.”   What do you know “Vince” tag has a partial print on it which belongs to…..Marcus Gates and they now have a real lead in the 3XK case.  They also find out that Gates, when in prison had a cell mate, Jerry Tyson.  

C&B go to visit Tyson in prison and he is visibly scared.  He says Gates used to protect him in prison and now he is on his own.   He is terrified of talking to the cops for fear of what will happen to him.  He says Gates is pretty powerful and can get to him, even from the outside.   Tyson eventually admits there is a bar that Gates likes to frequent in the Meat Packing District and that they should check that out.  They do and they grab Gates as he is leaving the bar.

Back at the precinct, they question Gates.  He is very calm, cool, and collected.  He is toying with Beckett during her interrogation.  This is also the first time Montgomery tells Castle, he can’t go into the interrogation room since Castle joined the team.   He also has a great scene with one of the previous victim’s father and you see how personal this is for Montgomery’s.   Gates is able to explain the fingerprint away (he works in a prop house where he touches almost all of the props) and he has an alibi for the time of victim #1’s death.  We know that isn’t true because we saw Gates on the street corner stalking the victim right before her death.    Beckett tells him they are in the process of searching his apartment and he wants to see a copy of the warrant.   Beckett unfortunately has to give it to him and he is able to see how much they know about the case.

Since Gates must have brushed up on Law 101 in prison, he informs Beckett that without evidence, they cannot hold him any longer and he wants to leave.  They check out his alibi and the camera outside his apartment shows him entering the building at 7:30pm and never leaving.  So he couldn’t have been the killer of victim #1..  They reluctantly release Gates and he taunts them a little on the way out.  Beckett immediately asks for round the clock surveillance on Gates.

At this point Beckett is desperate and needs some help.  He playfully teases her about how she needs him and he suggests going back to visit Tyson for another visit.  

This time, Tyson is really over-selling the “I’m afraid of Gates” card but C&B don’t see it.   They offer him a deal for his cooperation and information on Gates…early release from prison and police protection.  He takes the deal and starts to talk.   Tyson tells them that Gates mentioned about a time he was over this girl Sarah’s apartment (the daughter of the father who visited Montgomery earlier in the episode) and that things went bad.  To take himself off the radar screen for a while, he broke a bottle over someone’s head and that’s how he landed in prison.  Tyson is let out of jail and he is brought to a no-tell motel for safe hiding.  Here he tells Ryan that Gates had a partner for some of his crimes.  Ryan immediately calls Beckett and tells her the news.  

In the meantime, Tyson’s girlfriend has gone missing but Gates hasn’t left his building all night.  Gates has someone pose as him at the apartment for his “alibi” in front of the security camera.   When they look at it more closely Esposito asks if that is sweat he sees all over the guy’s head and neck.  It’s creepy sweaty dude!!!!  He was involved after all!!!!  

They plan to go get Gates when Monty comes in and informs them that creepy sweaty dude and Gates are now missing as well.  Uh oh.   This doesn’t bode well for Tyson’s girlfriend!  They figure out where Tyson’s girlfriend is and head straight there.  When they bust in they see Gates in the process of trying to strangle her.  Obviously, they arrest him and take him back to the cop shop.

Long story short the crew finds out that the link between Gates and creepy sweaty dude is that they are foster brothers and Gates is very protective of him.  Gates isn’t talking so they decide to use the fact that his brother is in the hospital after heart surgery as leverage to get him to talk.  It works and he ends up confessing everything to Beckett and asks for immunity for his brother who really just did what Gates told him to.  They agree and the confession is entered into evidence!!!  

As this is all going down at the station, Ryan and Castle are with Tyson to give him the good news…his girlfriend is just fine and they were able to save her from Gates.  While Tyson is packing his bag he asks “what about Gates.”  Ryan tells him he has been captured and arrested and all is now good.  Castle figures out that is a little strange and asks him why he didn’t ask about his girlfriend.  He is so concerned about Gates but why not his girlfriend who was almost killed? Tyson is really 3XK!!!!  As soon as Ryan and Castle show up at the no-tell motel and sees Tyson packing he yells “He’s 3XK!!!!”

Tyson’s then knocks out Ryan and ties Castle to a chair.  Castle then profiles his entire life history and how he led up to becoming 3XK.  Tyson then taunts Castle a little bit as well “You are always around death and murder.  What drew you to that?  What happened in your life that makes you want to be obsessed with death and murder?”   Just then, momma Castle calls.   Moms really have the best timing sometimes!!!!  Tyson warns Castle not to say anything that will tip her off or he dies.  They have their conversation and in the end Castle tells his mom he loves her.  They hang up.

Tyson has left the hotel and Beckett is right behind with the entire cop shop in tow.  They just miss 3XK but they are able to rescue Ryan and Castle and you can see the relief in Beckett’s eyes that Castle is alright.   When he asked her how they got there so quickly, she said Martha called her because when you told her you loved her, she knew something was wrong.   They get Ryan to the hospital and Castle is sitting out by the skeevy pool area.  Beckett sits down and asks him if he is ok and you can tell he is a little different after this experience.  She wonders out loud why 3K didn’t kill him.  Castle says to punish him.  He would know that he let the killer get away and that he is out killing more girls and it’s his fault.  Beckett says she knows exactly how he feels and they hold hands to comfort one another and end the show.