Halloween is just around the corner, but Hawaii Five-0 already has their Christmas episode in the bag.

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Filming for the untitled episode took place in early October and included appearances by Boardwalk Empire's William Forsythe and Suits Eric Roberts.

"Working w[ith] one of my favorite actors in one of my favorite places on earth. Hint: Forsythe & Hawaii," Roberts tweeted on Oct. 11 before teasing whether or not he will portray a bad guy for the Five-0 episode. "U'll hav[e] 2 watch 2 find out...But I'll tell u this ,full of surprises & 1 thing that is not a surprise is that Forsythe rocks."

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At the same time, Masi Oka (Max) gave fans a behind the scene's look at some of the holiday decorations going up around set (see photos above). It looks like McGarrett (Alex O'Loughlin) and his taskforce will need more than a little help from the ME and his new partner. Oka, O'Loughlin, and Scott Caan (Danno) can be seen hanging out in the morgue as Amanda Setton (Dr. Mindy Shaw) looks at a victim.

Find out more when Hawaii Five-0 airs Fridays at 9 p.m. ET on CBS. Click the video below to see a preview for the series' next episode.