Castle - Episode 8.14 - Summer Glau to Guest - best f y

Summer Glau has signed on to guest-star opposite her onetime Serenity captain Nathan Fillion in a spring episode of the ABC drama, TVLine has learned exclusively.

Glau will play a smart, sexy and strong private detective who goes toe-to-toe with — you guessed it — Castle. She will appear in this season’s 14th episode.