Detective Nick Burkhardt (David Giuntoli) can only be pushed so hard, and in tonight's fifth season finale of NBC's "Grimm," he finally pushes back. As a Grimm, Nick keeps the peace between Wesen creatures and mankind -- but recently those lines have become blurrier. The organization Black Claw, composed of radical Wesen, plan to take control of the human government and bring back the old Wesen ways. They've made big power moves and recruited Renard to run for political office. They will stop at nothing to bring accomplish their agenda – even if it means using Adalind and Nick's son, Kelly, as bargaining chips.

Ahead of tonight's two-hour season finale, "The Beginning of the End," Giuntoli spoke to SPINOFF about shifting alliances, Nick crossing lines to save his son, the battle royal with Renard and Season 6.

SPINOFF Online: How crazy is the Season 5 finale compared to previous years?

David Giuntoli: Less of a cliffhanger, weirdly. The things that happen within the episode could have been three season finales. Everything happens. The last moment is a little less of a cliffhanger, but it's the most compelling ending we've ever had in one of our shows.

Nick developed feelings for Adalind. How betrayed does he feel by her actions lately?

I think Nick knows Adalind is being used. She's a pawn in a game. She needs, first and foremost, to protect the kids. One of them is mine. If she doesn't keep me in the loop, I'll be very upset.

Nick and Renard have been enemies, allies and even friends. Where do they currently stand?

We're not friends any more. There's stuff you will see in the finale. Renard is definitely out for power at this point and he will both literally -- and figuratively -- stab anyone in the back to achieve his ends. Nick is definitely no longer his friend.

Renard attempted to recruit Nick into Black Claw. Does Nick even consider that an option?

There's just no way. Well, there may be one moment when he's surrounded in the precinct. Bonaparte is in Nick's face. I don't think Nick would ever join Black Claw, but he would deceive to get what he needs.

What can viewers expect when Nick comes to blows with Renard?

It's going to be huge. When you see the finale, Nick and Renard come to a head. The stakes are very high and it's mano a mano. Matt Taylor, our stunt coordinator, is probably going to get nominated for an Emmy with these season-finale fights. There were a couple of days of shooting for each fight. It's very fun to do fight sequences. The actors have to do the action. It's not about the emotion as much anymore. It's all about fights and following the action.

Nick is obviously personally invested in this battle. In what ways do those heightened emotions make him reckless?

Nick has to have a slight voice of reason to achieve his goals. At this moment, he doesn't have a voice of reason at all. He is definitely emotionally charged. I think he's dangerous when there's too much emotion going on.

As a result, how much does Nick turn to his fellow Grimm, Trubel, and his friends for help?

He's not relying on her at all. None of his friends can help him. He's going to set them all free. He believes everybody might die at this point. Therefore, he has to let them all go save themselves and let Nick handle it. Nick is willing to die for everybody right now.

Wu discovered he can woge. Does that make him Nick's secret weapon?

If Wu can use his powers only when he has to, it's going to be such a help. Wu has always been the utility player and now he's even better. He can woge out and literally go ape shit on those Black Claw operatives. Pun intended.

Diana and Kelly are incredibly powerful for children. How are they handling the new family dynamic and surroundings?

Diana is in that stage of life where she is old enough to make decisions and young enough where kids test boundaries. They throw tantrums. Boy, the stakes are increased when Diana is this half-Hexenbiest, half-Zauberbiest. When she doesn't know boundaries, people lose their lives. You will see that she comes into play largely in the season finale.

Eve has been a wild card. She's totally unpredictable. How will she step up in the upcoming fight?

Nick cannot count on Eve necessarily, but you'll see Eve may be changing a bit. We might get to see a little wisp of Juliette once again.

What kind of lines is Nick willing to cross in order to rescue Kelly and put an end to Renard?

Nick is willing to do most anything to defeat Renard. Renard went to some place sacred to him, which was he stole Nick's kid. That's all I have left. That's the closest thing to family I have. My mother is gone. My aunt is dead. Juliette is gone. That child is the last thing I have. Renard has gone for him, so all bets are off. There's no limit to what Nick will do to get Kelly back.

"Grimm" was renewed for a sixth season, but a shorter one. In what way does this finale set things up for next year?

Season 6 is going back to the main characters -- less so on the evils that are just a little off camera, like these Black Claw organizations -- and more on the eight or so main characters and what the five previous seasons have set up for us. There's so much to play that we don't have to gloss over it. We can fill 22 episodes of dealing with the consequences. They won't be glossed over. Did Juliette kill my mom? Did Juliette do these terrible things when she was Eve or was she just Eve? And Nick has a child with their sworn enemy. So, who is who? What is what? Who is to blame?

Our show is largely about monsters that lie within people and not to look at those things so black and white. There's a grey area. Monroe is a Blutbad, but he's trying to keep his evil urges at bay. In another era, I would have lopped his head off. But, he's trying to be good. Nick has it in him to see grey and that's what our show is a little bit about.

The two-hour season finale of "Grimm," titled "Beginning of the End," airs at 8 tonight on NBC.