Stana Katic, Nathan Fillion
In the exclusive clip below, the pair's investigation into the work of what turns out to be a serial arsonist leads them to the home of a pyromaniac who runs a website for people who have fire fetishes. And the case quickly turns personal, when Castle and Beckett discover that Esposito (Jon Huertas) and Ryan (Seamus Dever) may be in danger -- or worse, dead.
Check out a sneak peek from the episode below:
Castle airs Mondays at 10/9c on ABC.