Meanwhile, Monroe (Silas Weir Mitchell) and Rosalee (Bree Turner) are packing and preparing for their delayed honeymoon.
Nick and Hank meet with Juliette (Bitsie Tulloch) to know more about El Chupacabra, she explains that her grandmother told her stories about it.
Juliette reveals to Rosalee that she took the pregnancy test many times and she wasn't pregnant but is told to go to a doctor if the symptoms continue.
After she leaves, Rosalee receives a chilling telephone call and a mystery voice tells her, "You made a mistake".
The next day, Diego loses control of the disease, attacks Gabe in his office, escaping while still transformed.
With DVR factoring in, the episode was watched by 7.86 million viewers and had a 2.3 ratings share in the 18-49 demographics.
Kathleen Wiedel from TV Fanatic, gave a 4.9 star rating out of 5, stating: "Well, I can safely say I did not see that twist coming.
"[4] MaryAnn Sleasman from TV.com, wrote, "'Chupacabra' was a strong episode as far as fall finales go, and let's be frank, Grimm has never really suffered from the sort of 'pre-hiatus letdown' issue that so many other series often struggle with; the show always tends to deliver the goods, be they in the form of zombies or monster babies or beheadings.
"[5] Christine Horton of Den of Geek wrote, "The mid-season finale is upon us already, and could easily have the alternate title, the one where stuff happens.