The actor has signed a new deal to return, but boss David Amann will be exiting ahead of a potential renewal.

ABC's Castle took one big step closer toward an eighth season and another step back.

On the plus side, star Nathan Fillion — rumored to be ready to move on from the series — has signed a new deal to return to the veteran procedural, The Hollywood Reporter has learned. On the negative side, showrunner David Amann will not be returning to the series he has overseen for the past year.

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Meanwhile, co-star and Fillion's leading lady Stana Katic, has yet to re-up for a potential season eight, as rumors circulate that the series could return for a final, 13-episode run.

While news of an official renewal will come closer to the Disney-owned network's upfront presentation to Madison Avenue in May, a deal for star Fillion certainly paves the way for the detective soap to return — with a new showrunner. A replacement for Amann has not yet been determined.

Amann has been sharing Castle showrunning duties since the start of season seven, working alongside Andrew Marlowe — who had overseen the Monday staple since its freshman run. Marlowe, while still an EP on the drama, focused on development via his deal with Castle producer ABC Studios.

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In August, ABC announced it was developing a potential Castle spinoff with Marlowe, his wife/Castle writer/exec producer Terri Miller and Missing's Gregory Poirier, based on the Derrick Storm series of mystery novels written by Richard Castle, the fictional author portrayed by Fillion. The project did not make the pilot cut. For their part, Marlowe and Miller also developed a drama about Raymond Chandler's famed detective Philip Marlowe for ABC in 2013 that is still in contention.

Produced in-house by ABC Studios, Castle has been a sturdy performer for the ABC on Mondays at 10 p.m. and still pulls 12.7 million viewers on a weekly basis.

Keep up with all the renewals, cancelations and new series orders with THR's handy Scorecard.

Email: Lesley.Goldberg@THR.com

Twitter: @Snoodit