Grimm has conquered a lot of wesen and seen a lot of woges over the course of five seasons and 100 episodes. NBC's horror series airs its centennial episode on Friday and, in addition to a lot of action and big breakthroughs, it'll have a major effect on the show's current central couple.

Nick (David Giuntoli) and Adalind (Claire Coffee) are still trying to figure out how to define their relationship and feelings for each other in the middle of a war between the uprising wesen in the Black Claw and the government-controlled Hadrian's Wall. They slept together right before Nick left for Germany with Monroe (Silas Weir Mitchell), but that leads to more questions than answers in the milestone episode.

Grimm: Welcome to awkward car conversations with Nick and Monroe

"[Having sex] complicates things, certainly, especially after what we learn about Adalind in the 100th episode," Coffee tells "It complicates things even further because [Adalind's daughter] Diana is going to come back into the picture."

While Nick and Monroe may get lucky in Germany, they'll find that the stakes have only gotten higher at home after someone attempts to assassinate mayoral candidate Andrew Dixon (Michael Sheets). The additional distractions will only make it that much harder for Nick and Adalind to figure out what they mean to each other.

"For Adalind, the feelings are definitely genuine," Coffee assures. "They can't quite trust that the feelings are real outside of these circumstances. These are very stressful, dramatic circumstances and people do very dramatic things."

Grimm's 100th episode airs Friday on NBC at 9/8c.

Watch: Grimm's 100th episode will unlock all the answers