Castle - Kill Switch

An investigation into the murder of a government investigator leads Esposito (Jon Huertas) to be taken hostage in a subway car with more than a dozen other hostages by a cyber activist whose motives, including plans to target a group of one-percenters and demand the release of his incarcerated girlfriend, seem more about buying time than getting the demands actually met. Through a hidden surveillance camera the 12th Precinct can observe events on the subway car while Castle (Nathan Fillion), Beckett (Stana Katic), and Ryan (Seamus Dever) race to find answers as to what is really going on.

Although the true motivation for poisoning the suicide bomber with a rare flu strain are a bit over-complicated (forcing the show to rush to wrap-up the reveal), the tension delivered in "Kill Switch" works well leaving the show's stars helpless to protect one of their closest friends. The episode also brings up the unresolved issues in Esposito and Lanie's (Tamala Jones) relationship and introduces a possible new romantic interest for the detective (even if the episode's epilogue seems to immediately squash the possiblity of her return anytime soon).

Huertas steps up to do most of the work while the rest of his co-stars really take a backseat this time around. Episodes not centering around Castle, Beckett, or the pair's relationship tend to be a bit hit-and-miss. I wouldn't rank "Kill Switch" among the show's better episodes, but it works for a mid-season episode that (hopefully) may move Esposito and Lanie's relationship off the back burner and give both characters more interesting B-story options.