Castle (Nathan Fillion) and Beckett (Stana Katic) work with a Fire Investigator (Wendy Davis) to discover the identity of a serial arsonist responsible for the murder of her partner and the torching of a building belonging a former member of the Italian Mob. When Castle finds a video of the fire taken by “The Phantom,” NYPD tech Tory Ellis (Maya Stojan) helps trace back to a fire fetish site online. Following the victim’s notes on”The Phantom” leads Ryan (Seamus Dever) and Esposito (Jon Huertas) to the arsonist’s home base where they accidentally trigger, and become trapped, in a massive explosion.
With their loved ones missing and presumed dead Lanie (Tamala Jones) and a very pregnant Jenny (Juliana Dever) arrive on-scene just in time for Ryan’s wife to go into labor and her husband to throw up a Hail Mary and give Castle a clue to how to get them out of the burning building alive. Meanwhile a talk with a member (Ethan Cohn) of the online group gives their Fire Investigator a clue to nabbing their arsonist as well.
Let me take a moment to first applaud the show for showcasing the importance of the birth of Ryan and Jenny’s daughter (who thankfully isn’t going to be a white Irish Catholic boy named Javier) without making it the focus of the episode. I’m not surprised to see both detectives make it out of the burning building alive, but the episode made me buy the possibility that one, or both, might not. As to the case itself, the search for the arsonist takes a backseat during the final half of the episode, and the wrap-up is a bit anticlimactic given the stakes of the rest of “Under Fire.”