I can' remember for sure on the DNA, but did they have something on the bullet that hit Beckett? I don't know how that would be possible, but that's about the only thing I can think of. Even the best shows will have a little hole in the plot once in awhile.
I get the principle of the thing, but I'm still not sure how Esposito could be ****** at Ryan for bringing in the cavalry, especially considering that it literally saved Beckett's life. That should make for a good start to next season. The writers have really done a nice job of weaving this plotline in with the "regular" episodes. It'll be interesting to see how high this thing with Beckett, her mom, Capt. Washington, etc goes up. They've left themselves some great teasers to work with.
Overall, I thought it was another great episode. I think I could watch this show every day of the week and not get tired of it. You go from one like the Zombie episode last week that was full of laughs, to one like last night that was wall to wall tension and it still entertains you either way. There aren't a lot of shows that are appointment viewing for me, but Castle is absolutely at the top of the list. It's gonna suck waiting months for a new episode.
And below was my reaction to how hot Beckett looked when Castle opened the door....