David Giuntoli David Giuntoli

Grimm fans don't have to wait until Thanksgiving to feel thankful.

Viewers can "Thank Grimm It's Friday"  with the series' fall finale (9/8c, NBC), in which Det. Nick Burkhardt (David Giuntoli) is a man possessed when he finds out that his cop partner Hank (Russell Hornsby) has been pummeled to a pulp. Apparently, that impotent Hexenbiest Adalind (Claire Coffee) has hit Portland and has set her sights on those Nick holds near and dear. Speaking of, his girlfriend Juliette (Bitsie Tulloch) — whose selective amnesia has set back their relationship — is adding to his stress levels with her obsessive attraction to Capt. Renard (Sasha Roiz).

PHOTOS: Everyone is posing nude!

It's a big, twisty, cliff-hanger episode, and Giuntoli shares his excitement for "The Season of the Hexenbiest" with these seven reasons to "Thank Grimm It's Friday":

1. Crazy-Eyes Adalind is back: "I love Claire Coffee, and she's a regular now on the show, which has just been thrilling to everybody," Giuntoli tells TVGuide.com "Her character Adalind, on the other hand, is vile and just soulless — literally since I French-kissed her soul out of her body last season. Claire has been reading books about psychopaths because Adalind is a bad human being. She loves being bad. She takes kind of a mischievous, gross joy in getting power, destroying my relationships and whatever it takes to get what she wants. She's got that flirt-hate going on, which is dead sexy."

2. The secret is out ... sort of: Which secret? There are so many! Well, Juliette and the captain's lust does not go unnoticed by Monroe (Silas Weir Mitchell), who walked in on them smooching at the end of last episode. What comes of that remains to be seen. "I wonder of Monroe will tell me," says Giuntoli, who muses that even if Nick were to find out the truth, "he'd be the angry-jealous type."

3. Monroe's nose knows: "Monroe is part of my crime-fighting team. He comes out and does some recon for me," Giuntoli says. "He has this tremendous sense of smell and this tremendous knowledge of Wesen history because he's this crazy history buff. Those skills come in quite handy. He can kind of sniff out who's there and tell me what that might mean." Monroe's nose leads them to the Hundjagers, whom Giuntoli describes as "the henchmen for the Verrat. They're the people who get sent out to do the real high-end dirty work for the powerful people in Europe and the royal family."

Grimm's Juliette to unleash "mad bedroom skills" — but with whom?

4. Nick embraces his inner vigilante: "Even though we're cops, we go rogue more often than not now," he says. "We're always willing to cross the line, whereas last season I was very reluctant to cross that line." Besides, is Nick just going to let the Wesen who took out his partner go unpunished? "When Hank gets beaten up, oh yeah, I feel fairly responsible," he continues. "But I'm just pissed off more than anything. When Monroe asks, 'What do you want to do?' I tell him, 'Let's rub these guys out!'"

5. A shiny new toy:  Hold the crossbow! Nick debuts an intriguing new weapon from the trailer's arsenal. "I love how Nick  has a bevy of intricate medieval weapons in the cabinet, but he picks the baseball bat," Giuntoli says. "It's a baseball bat with some lovely details on it. Baseball was the only sport that I could even remotely perform well as a child because I had a low center of gravity."

6. That won't leave a mark! "I get injured often in these [fight] scenes. I've had so many scars from Grimm, but luckily, 'The Season of the Hexenbiest' is not one of them," he says. "The Hundjager fight was pretty easy for me because you're not doing any crazy twists or turns with your body."

7. Fan feedback: Although Giuntoli is often shooting Grimm on Fridays into the wee hours and therefore isn't able to watch the episode live, he makes a point to check out what the viewers are saying online after filming wraps for the day. He especially enjoys the responsiveness of Twitter where he shares his thoughts as @MisterGiuntoli. "We have some hardcore fans," he says. "I love getting on there and bantering and winding people up or letting them wind me up. We like to provoke each other. It's like this great, fond relationship I have with my Twitter fans. Everybody always asks me two things: 1) 'Will you marry me?' (I just say yes), and 2) 'When will Silas get on Twitter?' So just yesterday I tweeted that Silas was on Twitter, but I wouldn't give out his handle. And they were all freaking out. And then I said, 'He got sad, guys, and he deactivated his account already.'"

Check out this preview of Grimm's midseason finale, which airs Friday at 9/8c on NBC, and then share why you "Thank Grimm It's Friday" in the comments below.