I have to agree with one of the comments earlier that there are quite a few loopholes in the storyline. If the former CIA is one of their best, why only send one person to apprehend him? But I have to say that the storyline about the linchpin is interesting. Hm... just one weak link.. who may it be?
Beckett is funny when she gets insecure about Castle's former short-term partner/girlfriend of one year!!! haha, that was hilarious when Beckett asked how short was short!