In the latest episode of NBC's "Grimm" titled "The Rat King," it seems that the mythological Rat King monster is at large and has killed two people.

CLICK HERE to watch the mystery behind the Rat King and why he is on a killing streak.

According to the synopsis of the episode, two people turn up dead at a local Portland dump after they encounter what appears to be the mythical Rat King. Meanwhile, Nick meets Meisner after taking an injured Trubel to the hospital.

The synopsis mentioned that when a couple of people go sneaking around to find the whereabouts of Rat King, they ended up dead, allegedly killed by the monster.

Nick and Hank become involved with the case when the Portland P.D. comes for the assistance. According to the picture posted on the site, Nick, Hank, Monroe and Selina Golias (guest star Carlson Young from SCREAM) are gaping at a gigantic creature when they come across it. Hank is carrying a rifle with him.

The promo video, posted by CDA News, states that Hank is saying "I don't like rats" while shooting at the huge creature whom all of them call "Ratzilla." The place looks like a junk shop.

Meanwhile, Nick will be investigating the case both as a cop and as a Grimm as he suspects that the creature is a Wesen and is loose on the streets of Portland. Besides it, Nick will also have to handle his personal issues when a tired and injured Truble shows up on his doorstep.

After hospitalizing Truble, Nick will meet Meisner and both of them will have a fight as mentioned in the poster.

Apart from it, in an interview with Blastr, series creator and executive producer Jim Kouf has said that the 100th episode of the series will focus on the keys. Norberto Barba, executive producer and director, also said, "Nick and Monroe go on a big trip because of the keys, and they find where the keys are. We see what the keys fit and we find out what's in that, and it's mind-blowing. It will change things."