Castle Preview: A 'Deeply Emotional' Episode Explores a Cop's 'Worst Nightmare'

This week on ABC’s Castle (Monday, 10/9c), Detective Kevin Ryan gets blindsided by a blast from the past, when the gun the 3XK killer stole from him almost exactly a year ago resurfaces in the grimmest of ways – as the weapon used to kill a young woman.

“It’s a deeply emotional episode for Ryan,” series creator Andrew W. Marlowe shares with TVLine, explaining that such a deadly scenario is “the worst fear of any cop.”

Seamus Dever, who plays Ryan, concurs, telling us, “It is anyone‘s worst nightmare, that something that was your responsibility has now been used to kill somebody.”

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But rather than let this tragic twist sideline the NYPD detective with all-consuming guilt and grief, Castle uses it to present a Kevin Ryan like we have never seen before.

“We did an interesting thing,” Dever reflects. “[Director] Rob Bowman didn’t want Ryan sort of wallowing in the fact, ‘Oh, this happened to me. Poor me.’ Instead, he wanted to activate Ryan to be a better cop, to do his job but even better than he ever has before.” As such, Ryan and the team work hard and fast to track down his weapon before it can be used again.

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Despite the dark subject matter, Dever says, “It was fun to really work on that side of Kevin Ryan, because we don’t get to see those shades of him too much.”

Alas, stepping to the fore of this episode did come with a small price.

“I had Nathan Fillion hours!” Dever fake-laments with a laugh, referring to Castle’s portrayer. “That means [shooting for] 14 hours, taking time to go home, memorize more lines, come back the next morning and do it all over again. You feel like you live here!”