Grimm Grimm

David Giuntoli may play homicide detective Nick Burkhardt in NBC's fairy tale-tinged crime procedural Grimm, but in real life, he's not that stoic when faced with corpses — especially the fake ones used on the series.

"I'm not usually easily disturbed, but I've walked on the set and been absolutely disgusted to my core," he tells "I'll always remember where I was when I saw this specific crime scene [in 'Danse Macabre']. There were rats crawling out of the stomach, out of the mouth of a corpse. The corpses, the prosthetics are so real that until you touch them, your brain doesn't understand that it's fake. It's terrifying. There's a lot of eating lunch in my trailer far, far away from the morgue set."

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Luckily for Giuntoli, Friday's Rapunzel-inspired episode (9/8c, NBC) is relatively light on the gore. The episode, titled "Let Down Your Hair," gives a nod to the classic fairy tale, about a kidnapped princess with magically long hair. "It's one of those stories that is more emotional, less 'chop off the head of the bad guy,' which is nice," Giuntoli says. "There's a murder... of a guy who was growing tons of marijuana and selling it. We don't know who kills him. But we find a strand of hair at the crime scene that turns out to belong to this girl who has been missing for nine years."

The case holds particular significance for Nick's partner Hank (Russell Hornsby). "Hank has an emotional through line here. He's been... a detective much longer than my character," Giuntoli says. "He was part of the original team investigating the missing girl nine years ago, but he had to deal with the family and tell them that she hadn't been found. When we see this girl's DNA [at] the crime scene, it's a big moment for him. He has a lot invested in finding this girl."

Check out this clip of Hank learning about the DNA:

Like Rapunzel, missing girl Holly Clark (Mary Nelson) also has long hair that's been made unruly by living in the wild. Or is there more to it than that? "I see what looks to be a feral child out there that everyone thinks is just a missing girl," Giuntoli explains. "Only I think it's also possibly a creature. I don't want anybody else to find her first because she's been feral all her life and therefore [is] dangerous. But I still have this huge tug in my heart to save this girl, so I enlist Monroe."

Reformed Blutbad Monroe (Silas Weir Mitchell) has learned to suppress his inner wolf, and thus is called on as Nick's liason with the creature world. "He wants to help me get the bad guys because he knows that not everybody's bad," Giuntoli says. "He's not bad in his core because he fights these urges. He knows it's a choice. It's kind of a love story with this girl and Monroe — not love in a romantic sense, but love in that they understand each other."

Meanwhile, Nick is dealing with his own love woes, namely his relationship with girlfriend Juliette (Bitsie Tulloch), who's in the dark about Nick's calling as a monster profiler. "I'm lying to her, and worst of all, the danger is getting closer and closer to the home front," Giuntoli says. "There's a huge amount of guilt involved with that. Basically, if I tell her that I'm a Grimm, she's going to think I'm crazy, and I don't want her to leave me. Not telling her is a very selfish thing, though, because she can't prepare herself for the monsters that are trying to get me."

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Despite his misgivings, Nick isn't able to deny his Grimm heritage. "Throughout the series, he does kind of summon up the DNA from his ancestors," Giuntoli says. "He has to learn how to physically fight these creatures. Dealing with the monsters and catching the bad guys is becoming more and more natural to him. It's something that his family's done forever. And I think it's something that when he heard he was one of the Grimms, it made a little bit of sense to him."

The actor, who is currently shooting Episode 13 in Portland, promises more explanation into the Grimm lineage. "The mythology is pushed forward in a large way in this episode," he teases. "I learn more about my history, about my aunts, about my parents."

Grimm airs on Fridays at 9/8c on NBC.

In case you missed it, check out our video interview with Giuntoli: