Nathan Fillion to return for season eight of 'Castle'

LOS ANGELES, April 17 (UPI) -- Nathan Fillion has signed on for season eight of Castle.

The 44-year-old actor will return as mystery novelist Rick Castle should the ABC series be renewed. The crime drama premiered in 2009, and is expected to be picked up for an eighth season in May.

Showrunner David Amann, however, will not return for a new season. The executive producer replaced series creator Andrew W. Marlowe as showrunner in season seven, and the status of Marlowe, who remained as an executive producer, is uncertain.

Co-lead Stana Katic's future with the program is also unclear. The 36-year-old actress has portrayed Detective Kate Beckett opposite Fillion as Castle since the show's debut, and is reportedly still in contract negotiations with ABC.

Castle is in the midst of a seventh season, and airs new episodes Mondays at 10 p.m. ET. The series sees Castle and Beckett collaborate on solving unusual crimes in New York City, and also follows their developing romance.