For the second straight season, "Castle" sits on the ratings bubble. The showrunners again face the difficult task of writing a season finale that could also serve as a series finale, but Terence Paul Winter and Alexi Hawley haven't given up on the show's chances for a ninth season.

"We think the show has a lot of life in it," Hawley told TVLine, "as do these characters."

Hawley and Winter took over the showrunning reins from David Amann, who served as the position last season, inheriting the post from "Castle" creator, Andrew W. Marlowe. Marlowe and his wife, Terri Edda Miller, wrote last year's season finale and tied up loose ends just in case ABC didn't renew the series for the 2015-2016 schedule.

"Andrew and Terri wrote it as if it was the series finale," Winter told TVLine, "and there's a very good chance that we'll most likely be doing that here. We hope to come back for Season 9, but we have to act as if [we might not]."

"Castle" faced major fan backlash earlier this season when it decided to split its two main characters, Richard Castle (Nathan Fillion) and Kate Beckett (Stana Katic), after years of will-they-won't-they and a delayed wedding. The showrunners stuck to their guns and quietly reunited the couple in the midseason finale, although publicly they are still separated.

"We do feel energized by the shake-up and what it has allowed us to do," Hawley said. "We've tried to have a lot of fun in and around an obviously emotional subject... We're really happy with the results."

"Castle" will resume its eighth season on Monday, Feb. 1 at 10 p.m. on ABC.