Viewers

The episode was viewed by 4.74 million people, earning a 1.1/4 in the 18-49 rating demographics on the Nielson ratings scale, ranking third on its timeslot and fifth for the night in the 18-49 demographics, behind 20/20, The Amazing Race, Beyond the Tank, and Shark Tank.^[1] This was a 12% increase in viewership from the previous episode, which was watched by 4.21 million viewers with a 1.0/4.^[2] 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.

Overall, the fourth season of Grimm averaged 6.98 million viewers, which is a 13% decrease from last season, which averaged 7.97 million viewers.^[3][4]

Critical reviews

"Cry Havoc" received mostly positive reviews. Les Chappell from The A.V. Club gave the episode an "A−" rating and wrote, "'Cry Havoc' benefits from this late season narrative inertia, as it's an episode that's constantly in motion. Picking up immediately from the 'Headache' cliffhanger of finding Kelly's head in the box, Nick and the rest of Team Grimm are on the warpath immediately. You can always tell on Grimm how bad things have gotten by the degree to which these officers of the law disregard the law part of the equation, and it's jettisoned right away as the Trubel-severed Verrat head winds up in Wu's car trunk. Here though, it's a mix of enforcing the law and subverting it, as they use the head and Adalind's cooperation to set Kenneth (or rather Kenneth Alun Goderich Bowes-Lyon, according to his passport) up as a creepy head-taking killer. It's interesting to see the case-of-the-week beats playing out in a different framework, even as you wonder why no officers are able to connect Adalind to the dozen or so crimes she's been connected to since the start of the series."^[5]

Kathleen Wiedel from TV Fanatic, gave a 4.8 star rating out of 5, stating: "'Cry Havoc' followed a really simple, straightforward plot. There was no case of the week this time, and almost everything that happened fed into the A-plot (otherwise known as the Save Diana plot). The only B-plot was really Renard dealing with the aftermath of Jack. The lack of distractions really worked in this episode's favor. The story was fast-paced and adrenaline-fueled... and surprisingly took place entirely in one night! As Bud put it."^[6]

MaryAnn Sleasman from TV.com, wrote, "Like the best kind of season finale, however, 'Cry Havoc' left me wanting more and eager to see what kind of world Nick and his allies exist in without Juliette, his mother, and his vast library. Three of the biggest support systems that held Nick up were decimated and the effect on Nick was apparent immediately. The freshness of his wounds made Nick's thirst for revenge much more ruthless and with time that razor-sharp brutality should dull. But Nick's losses here were so great and so sudden that this was the sort of situation where he needed his foundation the most. What kind of Grimm is he going to be next season? And, more importantly, what kind of human being?"^[7]

Christine Horton of Den of Geek wrote, "This was a satisfying end to a series that perhaps dragged out one or two story arcs longer than it should, and maintained its 'Wesen of the Week' sub-plots when we really wanted more focus on the developing storylines among the main characters. (However kudos to the writers for the Wesenrein story arc, which delivered well above any other Wesen-based tangents this season.) Grimm picked up the pace over the last few episodes, neatly tying up some loose ends. If anything season five should pick up where this episode left off, and let the show continue to explore its darker side."^[8]