If you have missed the first two episodes of Castle on ABC, just know that you shouldn't be missing them.
Great show and since it has Nathan Fillion you know that it has some great comedy bits, but the story is good.
You should be able to catch old episodes on the shows main site here:
http://abc.go.com/primetime/castle/ Basically it is an author who is doing research for a new book series so he is following around a NYPD detective. Sounds like a snoozer, but trust me it isn't.