'NCIS' Stars Wilmer Valderrama and Sean Murray Tease 'Unexpected' Finale Cliffhanger

NCIS finishes up its historic 20th season Monday night, but it's not the end of the story. Stars Wilmer Valderrama and Sean Murray teased an "unexpected" cliffhanger for the episode, titled "Black Sky." The show has already been renewed for another season, so the writers weren't forced to rush tying up loose ends.

"It's amazing. I mean, the fact that we're not only still here we've got the incredible support of our fans who have been with us from the get-go pretty much and are still with us and still going," Murray told Entertainment Tonight. "We're gonna keep plugging away as long as they let us." Murray joined the show as Timothy "Tim" McGee during Season 1 and was promoted to a main cast member in Season 2. He is one of the last remaining stars from the first season, alongside David McCallum and Brian Dietzen.

The NCIS cast today is led by Gary Cole, Wilmer Valderrama, Diona Reasonover, and Katrina Law. In "Black Sky," Valderrama's Nick Torres finds himself behind bars as the team tries to stop a terror attack on U.S. soil. CBS let the show "do something really loud" with the finale, Valderrama told ET. "We do a major cliffhanger and it's not just the case that has to close, it's actually a new chapter -- a dark one -- that may open up for Torres, as well as how it affects all of us as a team and as a family."

Torres is even going back to his rogue roots, as he finds himself on the wrong side of the law. "There is something that happens towards the end of this episode that you don't see coming," Valderrama teased. "We might get the bad guy of this episode, but we introduce another big bad [by the end of it]."

"The fans are going to be left with quite the cliffhanger," Murray chimed in. "We always like to end on usually something that's going to leave little tastes and we'll see where we come back to." Law, who plays Jess Knight, said the cliffhanger is "unexpected," and "makes you wonder what's going to happen." Even Law was surprised by how "dark and deep" the episode goes.

NCIS is a spin-off of JAG and is now the third-longest-running scripted show in U.S. broadcast history, behind only NBC's Law & Order: Special Victims Unit and Law & Order. The show spawned three finales, including the just-ended NCIS: Los Angeles. It will return for Season 21 in the fall, alongside NCIS: Hawai'i's third season.

"The fact that this show 20 years later, can still not only be welcome in people's homes, but be still up and running and still be swinging and everyone's still happy to be here," Valderrama told ET. "Still excited to keep swinging and the writers are still keeping it fresh, and the actors are not tired is a testament to the efficiency and most importantly the love that everybody puts into this. We like it here and we have a lot of fun."

NCIS airs on CBS Mondays at 9 p.m. ET, with NCIS: Hawai'i following at 10 p.m. ET. Both shows are available to stream on Paramount+, alongside NCIS: Los Angeles, NCIS: New Orleans, and JAG.