The Hawaii Five-O team lands a very unique case that they are unprepared for in the Friday, Dec. 20 episode.

The preview for the upcoming 11th episode, Pukana, starts with the team investigating a death at a vehicle dump yard. They are seen analyzing a decaying dead body in the trunk of a car that has a bullet wound to its head. The guys assess the injury was done "execution style."

"There goes our holiday," exclaims Chin Ho Kelly (Daniel Dae Kim) while looking at the body.

On the surface of things it seems like the guys have a grasp of the case, but the preview clip shows the detectives later being completely thrown off by something kept in a safe. 

"They've seen it all but nothing could prepare them for what's inside the safe," runs the tagline for the episode. As snippets of the team's progress in the case are shown, the clip ends with Steve McGarrett (Alex O'Loughlin) opening a safe. He illuminates the interior with a torch but immediately slams it shut as Dano 'Danny' Williams (Scott Caan) and Captain Lou McGrover (Chi McBride) look on from behind.

The clip effectively builds the anticipation, keeping most facts under a shroud of mystery.

The show's ratings took a bit of a hit over the past weekend as it did not have any Christmas special lined-up. Hawaii Five-O slid 20 percent from its last original three weeks back. Deadline deemed that as being a series low for the island cop show. 

The new episode airs Friday, Dec. 20 at 9 p.m. E.T. on CBS

Watch the preview here:

Tags: Hawaii Five-O Season 4