Nathan Fillion has signed a one-season contract to return to "Castle" season eight, but his co-star and TV wife, Stana Katic, remains undecided on her future with the ABC show.

If Katic chooses to leave the series, she won't be the only one. Showrunner David Amann will relinquish his post of one year at the end of this season, according to The Hollywood Reporter. He took over the position from "Castle" creator Andrew Marlowe, who oversaw the crime procedural for its first six seasons.

Marlowe stuck around to write a few episodes, this season, but mainly stayed focused on developing new projects for ABC Studios. He may put his entire focus on development moving forward and step away from his writing and producing responsibilities on "Castle" as would executive producer (and Marlowe's wife) Terri Edda Miller, according to TVLine.

Fillion and Katic have starred as the crime-fighting duo Richard Castle and Det. Kate Beckett for seven seasons. The will-they-won't-they couple finally got together at the end of season four and tied the knot earlier this season.

ABC has yet to decide whether it will renew or cancel "Castle."

According to TVLine, the seventh season finale is titled "Hollander's Woods," and the synopsis reads: "A death in the woods draws Castle back to a terrifying and defining event in his childhood. Investigation leads to obsession, as he attempts to unearth answers that have eluded him for decades, all while Beckett faces a crossroads."

"Castle" airs on Mondays at 10 p.m. on ABC.