It wasn't perfect, but "El Cucuy" has definitely been the highlight of Grimm's third season for me so far. It's Wesen-o'-the-week (who possibly wasn't a Wesen?) was pretty good, the plotting was solid and it actually felt like actual things were happening beyond the scope of the case — not much, but at least a little.
Two luchadores (okay, they're actually just thugs wearing luchadore masks, but I prefer my version) rob a gas station and kick the hell out of the 18-year-old kid working there. At the hospital, the kid's Latina mother prays for the thieves to get their asses kicked, so they don't make any other mothers sad. This is basically the hotline to El Cucuy, a Latino boogeyman who, in the universe of Grimm, at least, kills bad guys for moms.
El Cucuy comes and tears the throats out of the bad guys, repeatedly (it's very messy). Nick and Hank are pretty sure that wild dogs did it, but they do quickly concede it could have been a Wesen, so they are making some progress there. Meanwhile, they meet a former Marine named Florez at the crime scene, who wants his crime-ridden neighborhood cleaned up, although his plan to do this seems to be standing around crime scenes and yelling at the police they suck at their jobs. He is so very obviously El Cucuy.
Here's the bad part: We know the murderer is El Cucuy, because we saw it kill those guys, and the title of the episode is "El Cucuy." But Nick and Hank investigates this other dude with ties to the thugs, but who also has vicious dogs and he's a Wesen (a Hollentier, specifically), because of course he is. We know this is a major waste of time, but the episode keeps with it until minute 40, when El Cucuy kills a rapist while the Hollentier is in jail, and this new victim says the thing that killed her attacker looked like El Cucuy, which earns Nick a trip to Pilar to get schooled on the creature.
The Hollentier is released, and he immediately beats up Florez, who decides to retaliate by putting his Marine uniform and grabbing a knife — not a very El Cucuy-ish thing to do. Then Nick and Hank get footage of the bus the second victim exited, and see the same old sweet lady who was hanging around the first crime! You tricked me, Grimm! Well done there.
So Nick and Hank pick up the old lady, get a call that Florez is about to attack the Hollentier, drive by, and rescue Florez while the nice old lady gets out, transforms into a monster, and kills all the bad guys with a truly impressive amount of violence. It ends with the sweet old lady covered in blood, which is just as hilarious as it sounds.
Back at the precinct, the old lady flat out tells Nick he can't arrest her, because he can't reveal her true nature, and no jury would ever believed she brutally murdered six dudes, and besides, her work is done here (apparently the neighborhood crime wasn't quite as bad as Florez made it out). The end. Right there. Done.
• Things that happened that weren't part of the main story: Nick told Juliette about his mom. Nick's mom is in trouble in Slovakia but they can't do anything to help. Munroe told his mom about Rosalee. Adalind discovered her baby has two hearts. Renard learned Adalind's baby has two hearts.
• Juliette was exceedingly helpful this episode, wasn't she? It's nice, but wouldn't we all rather have Nick and Munroe back together? I feel like Munroe and Rosalee are being wasted as "Bosom Wesen Buddies," or whatever the hell is happening there.
• Munroe and Rosalee were shitting all over the Hollentier, calling their entire Wesen race vicious morons. Can Wesens be racist to each other?