This week's "Castle" takes place in a creepy alleyway where a homeless man comes across the body of the victim. Screams can be heard as the scene changes to Castle playing with dolls as he tries to gain inspiration for his next novel.
Castle finds this inspiration in the form of severed heads, a part of the case. Beckett, who is prepping for a trial, doesn't have the case, so Castle hops on the trail of the local gang unit police officer, Ethan Slaughter (Played by Nathan Fillion's "Firefly" co-star Adam Baldwin). Of course, it takes Castle giving Slaughter his jacket and promising a favor from the mayor in order for him to agree to let Castle shadow him.
All and all, Slaughter seems like a pretty nice guy (not!) and takes Castle to inform the family of their loss. After informing the father, they trail him to see if he'd take them to who actually killed his son. Castle calls upon the services of Team Beckett to see if they could identify the heads. They could, and Esposito also informs him that Slaughter has a reputation as the Widowmaker, as his last three partners have ended up dead.
After the phone call, Castle turns Slaughter only to see him drinking on duty. They enter a bar, and Slaughter basically instructs Castle to start a bar fight in order for him to nab his suspect. Castle does as ordered, and they gain their suspect. After the tense interrogation, they find out there's a turf war going on between two gangs.
Meanwhile, Beckett has a session with her therapist in order to find out why Castle is pulling away from her. Back with Team Castle, Slaughter unknowingly makes some inappropriate comments about Castle's daughter, who is currently working in the police morgue, while on stakeout. Castle, after informing Slaughter that he was talking about his daughter, slugs him after he continues to talk about Castle's daughter.
Slaughter finds the man he was trailing after this altercation and has Castle wait outside. Shots are heard, and Slaughter runs out and tells Castle that they were never there. Of course, later it is shown that Slaughter didn't kill the guy, but wanted to make sure Castle had his back. After a friendly round of torturing a Jamaican gang member in the city, it is revealed that there was a third gang involved that night.
Castle and Slaughter celebrate Castle's ability to stay alive a day with his new partner. Granted, seeing as with Beckett Castle had to stay alive while trying to not be tiger chow, this day wasn't exactly storming the beaches of Normandy.
The next day, Castle wakes up to a huge hangover and a very upset daughter who had found the letters from colleges that Castle had hidden to protect her. Later on, Castle is offered some more alcohol but refuses, opting for time to cure his hangover. They meet up with a member of the Mexican mafia, and wind up dead, but Team Beckett comes to the rescue. After some more intense interrogation of less than legal nature and some Beckett-Castle snooping, Slaughter catches his killer, and Castle is back with Team Beckett. All is right with the world ... after Castle makes good on his favors, of course.
Castle finds a new partner, but how will that affect his relationship with Beckett.
