Season
Season 8 Episode
- Season 4 Episode 1
- Season 4 Episode 2
- Season 4 Episode 3
- Season 4 Episode 4
- Season 4 Episode 5
- Season 4 Episode 6
- Season 4 Episode 7
- Season 4 Episode 8
- Season 4 Episode 9
- Season 4 Episode 10
- Season 4 Episode 11
- Season 4 Episode 12
- Season 4 Episode 13
- Season 4 Episode 14
- Season 4 Episode 15
- Season 4 Episode 16
- Season 4 Episode 17
- Season 4 Episode 18
- Season 4 Episode 19
- Season 4 Episode 20
- Season 4 Episode 21
- Season 4 Episode 22
- Season 4 Episode 23
Castle - Season 4 Episode 21 Headhunters
7.97 45 minutes With tensions rising between Castle and Beckett, Castle finds himself a new partner -- Detective Ethan Slaughter (guest star Adam Baldwin, "Firefly"), a tough and colorful cop from the city's gang unit. But Castle gets more than he bargained for when Slaughter shows him a grittier side of police work that puts Castle in the line of fire like never before
