Castle concludes it annual two-parter tomorrow night with Rick on the hunt for his daughter.

In the first clip from the compelling episode, we see a panicked Kate and Martha grow even more panicked when they realize they have no idea where their boyfriend/son is... until they get Rick on the phone and learn of his plan to find Alexis:

In the second sneak peek, we see Rick meet a man in the woods. He's a shadowy figure. He's mysterious. And his identity is unknown to our favorite author upon first exchange. But - SPOILER ALERT! - that will soon change in a big way.

Watch this key piece of Castle Season 5 footage now:

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.