TV Article Castle: Adam Baldwin returning in season 8 — exclusive By Natalie Abrams Natalie Abrams Senior Writer EW's editorial guidelines Published on August 13, 2015 09:17PM EDT Photo: ABC Adam Baldwin is making a return visit to Castle in the upcoming eighth season, EW has learned exclusively. Baldwin first appeared in the fourth season as Detective Ethan Slaughter, a rough cop with crude methods that Castle (Nathan Fillion) did a ride along with in the episode titled “Headhunters.” Details on what brings Slaughter back into the fold are being kept under wraps, but he’ll appear in an episode slated for early in the season. Just spitballing, but with Beckett becoming captain, Castle might need someone else to ride along with besides new addition Hayley Shipton (Toks Olagundoye). Castle returns Monday, Sept. 21 at 10 p.m. ET on ABC. •Castle First Look: Beckett’s got her eye on Rick in new season 8 poster •Spoiler Room: Scoop on Grey’s, Flash, Castle and more •Castle bosses reveal Beckett’s new job WANT MORE EW? Subscribe now to keep up with the latest in movies, television and music.