We only made it to season 4 finale, episode 23 tomorrow (here in Croatia). And still have to watch some missed episodes in s1 and s2 online.
This one was one dynamic episode, Slaughter dude was awesome, remember him from Chuck! That kind of roles suit him the best, crazy as* detectives or spies.
The thing that bothered me in this episode was, Kate "threatening" that Latino narco boss, that she will hunt him down, or whatever... oh, God, what was that? Totally unnecessary and not believable.