"Grimm" has been renewed for season 5 but before fans beat the drum and rejoice, they will have to get past the supernatural series' thrilling season 4 finale. Juliette has gone mad (she gifted her ex with his mother's severed head) and soon, Nick will go bonkers, too. 

It is in the final installment of the season titled "Cry Havoc" where the detective makes an outrageously outrageous discovery that prompts him to spring into action. The finale episode shows Nick "hell bent on getting revenge" on the Royals. 

Trubel's much-awaited return to Portland comes in handy for the vendetta-driven detective as she is going to be of help to him in taking vengeance. However, if series co-creator James Kouf's "but you don't really know it's her" statement to TV Line is any indication, there's some trouble there, too.  

Meanwhile, Juliette is growing more and more unstoppable and her Hexenbiest situation is becoming inescapable. Her ally is pushing her further into the dark, to an extent that she will never be able to return. Also, Juliette has baby Diana in her clutches and it is hard to imagine what horrors the veterinarian can do now that she herself is obsessed with settling the score with Adalind, and her dangerous alliance has gotten into her, almost controlling her. 

Speaking of Diana, Kouf recently told TV Line that before "Grimm" season 4 wraps up, Nick will learn that he is baby Diana's father. This will surely be one of the bombshells the finale is dropping. Carter Matt believes that the season may end with a cliffhanger. The trailer for the finale elicits terror as it foresees the future of everyone and harks back to the past that led to the very moment they are all in.

The season 4 finale of "Grimm" titled "Cry Havoc" will air on Friday, May 15.