Nick and his team will be challenged with taking down the mythical Rat King in next week's episode of "Grimm."

A synopsis for the upcoming episode, which is aptly entitled "The Rat King," reveals that Portland will come under attack by an overgrown rodent. In addition, Trubel will be hospitalized after enduring some type of injury.

"Nick (David Giuntoli) and Hank (Russell Hornsby) are called to the scene when three Wesen go out on a hunt at a local dump and get more than they bargained for when two turn up dead after they encounter the mythical Rat King. Meanwhile, a very badly wounded Trubel (guest star Jacqueline Toboni) is taken to the hospital and Nick finally meets Meisner (guest star Damien Puckler)," stated the synopsis, according to CarterMatt.

In the trailer video, Monroe (Silas Weir Mitchell) seems to be skeptical about the existence of the giant rat.

"Twenty-foot tall Ratzilla?" says a cynical Monroe. "It's not real."

However by the end of the video, he, Rosalee (Bree Turner), Hank and Nick are seen running for their lives as the rat appears to be terrorizing the city.

"We're going to need a pretty big trap!" shouts Monroe.

"Scream" actress Carlson Young will also join the team to combat the Rat King, notes TVLine.

Later on in the season, "Longmire" star Bailey Chase will make a guest appearance as Lucien Petrovich, who is the leader of a Wesen revolutionary group, reports Deadline.

Fans can also look forward to learning more about the origins and whereabouts of the mysterious keys in the 100th episode of the show.

"When we went to Comic-Con on the first year when we had no idea how long [Grimm] would run, we said, 'If we ever get to episode 100, we'll answer the question about the keys,' never thinking we'd actually ever have to answer because what show ever goes to 100? Then when we got to 90 and 91 and 92, we go, 'Uh-oh, we'd better figure out what those keys are.' So, I mean, we always had an idea, but now we had to actually do it. But yeah, we're going to deal with the keys in 100," said executive producer Jim Kouf, according to Movie Pilot.

The 100th episode, which is titled "Into the Schwarzwald," will air as Episode 12 next year. 

"Grimm" Season 5 Episode 4, "The Rat King," premieres on Friday, Dec. 4 at 9 p.m. ET on NBC.

Watch the preview video below: