Or, AUGH YOU CLIFFHANGERY BASTARDS part II. ^_^
So. The FBI team showed up really fast after the second murder, which made me wonder how exactly they got wind of what was going on. We didn’t see any sign of Beckett’s boss calling them in, so my best guess is that Agent Shaw and her team were already hunting the killer–and they followed him right into New York.
The fact that Agent Shaw took down the Hudson Valley Strangler is mentioned a couple of times in the dialogue, so I really have to wonder if this killer is that guy, perhaps recently escaped or something, and Shaw’s team’s been tracking him. This would also tie in with how we see Shaw in the trailer for the next episode with duck tape on her mouth; clearly the guy’s going to grab her at some point.
I totally also want to see Castle figure out how Shaw’s team showed up so fast, too, and to give her shit about it since that lack of information got Beckett in danger.