Mondays 10:00 PM on ABC
Castle
Watch Castle Season 4 Episode 21 online via TV Fanatic with over 2 options to watch the Castle S4E21 full episode. Affiliates with free and paid streaming include Amazon and iTunes.

Rating: 4.6 / 5.0 (283 Votes)

Episode Details

Castle Season 4 Episode 21: "Headhunters"

It's a Firefly reunion on Castle this week, as Adam Baldwin guest stars in the fun role of Detective Ethan Slaughter.

Castle Season 4 Episode 21 Quotes

Forget severed heads, I want to meet that guy!

Castle

Martha: Playing with dolls, are we?
Castle: They are action figures.

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