Hibernaculum (Grimm)

"Hibernaculum" is the 17th episode of season 4 of the supernatural drama television series Grimm and the 83rd episode overall, which premiered on April 10, 2015, on NBC. The episode was written by Michael Golamco and was directed by John Behring.

Plot
Nick, Hank, and Wu are called to investigate a series of frozen corpses and discover a rare Wesen that steals the body heat of its victims. Called a Varme Tyv (meaning "heat thief") these  poikilotherms (cold-blooded like amphibians and lizards) need to hibernate, en masse, to survive even moderate temperatures, or they too, freeze to death.

Juliette starts to feel she is losing her humanity as she seeks revenge against Adalind. Elsewhere, Captain Renard continues to suffer from frightening visions and mysterious bleeding, while Monroe works toward coming to grips with the Wesenrein incident.

Viewers
The episode was viewed by 4.76 million people, earning a 1.1/4 in the 18-49 rating demographics on the Nielson ratings scale, ranking third on its timeslot and seventh for the night in the 18-49 demographics, behind The Amazing Race, Hawaii Five-0, Last Man Standing, Blue Bloods, 20/20, and Shark Tank. This was a 5% increase in viewership from the previous episode, which was watched by 4.51 million viewers with a 1.0/4. This means that 1.1 percent of all households with televisions watched the episode, while 4 percent of all households watching television at that time watched it. With DVR factoring in, the episode was watched by 6.87 million viewers and had a 1.8 ratings share in the 18-49 demographics.

Critical reviews
"Hibernaculum" received mixed-to-positive reviews. Les Chappell from The A.V. Club gave the episode a "C+" rating and wrote, "It's difficult to pin down my feelings on this week's episode of Grimm, because more than any episode in recent memory, this is one where my appreciation of what's going on fluctuates wildly with every scene. The various twists in the case of the week were confounded by the way it stretched credulity, even by this show's standards. (How many corpsicles can you have in a city before reasonable people start asking what's going on?) Interesting parts of the Monroe, Renard, and Juliette stories were introduced and almost immediately pushed aside by the next scene. And for a weekly case that was succeeding on its own merits, it's infuriating to see the show get rid of its complexity in favor of trying to emulate The Walking Dead — the worst season of Walking Dead, no less. (Stupid farm.)"

Kathleen Wiedel from TV Fanatic, gave a 3.8 star rating out of 5, stating: "I have to admit, I got a good amount of guilty pleasure when Adalind realized that Juliette was hunting her. Yeah, not so fun when you're on the receiving end, is it, Adalind?"

MaryAnn Sleasman from TV.com, wrote, "One of the themes that consistently appears in Grimm's Wesen stories is the difficult balancing of existence in both the Wesen world and the human world. It's one of the reasons the show's universe has expanded to become increasingly complex and interesting, complete with monsters who are often more human than the humans themselves. However, it seems that lately, Grimm has focused much more heavily on unusual Wesen and dealt them some pretty terrible outcomes."

Christine Horton of Den of Geek wrote, "On reflection, Hibernaculum could be classed as one of the stranger episodes, even for a show based on fairytales."