I haven't seen one so far, so here is a recap of the 2 aired episodes ( Thanks for the Memories & Octopus Head) of Grimm season 4, which were really one story anyway.
We start season 4 exactly where season 3 left off, with Nick having lost his Grimm powers, Adalind having made herself look like Juliet to sleep with him to make that happen, Renard being shot several times by the rouge FBI agent who is really a wessen working for the royal family before he attacks Trubel and gets his head cut off in self-defense.
Season 4 picks up with Nick, Hank, Juliet and Trubel leaving the wedding, talking about how Nick isn't a Grimm anymore, and how that happened. They show up at his house to a crime scene full of cops and Nick and Hank convince Trubel to stick around, and admit to the basics of what happened, just leaving out the Grimm/wessen part. Then the FBI show up to reveal to the gang that the dead guy was one of theirs but he'd gone rogue. Meanwhile, Renard is in the hospital, possibly dying.
The scene outside the house goes like this:
We're introduced to the wessen of the week (and the next week), a guy who turns into an octopus head and uses the tentacles to suck the memories out of people, leaving them an amnesiac mess with bleeding suction marks. He uses this power to steal confidential information out of people's heads, and their memories become his.
In the meantime, while investigating the shooting and beheading at Nick's house, Woo finds the Grimm book! And Nick admits it belongs to him, but says it was just something passed down in his family and "they're just stories". The next person to find the book, is the female FBI agent, who of course turns out to be a wessen, so now she knows someone in the house is a Grimm. She puts the book someplace not in plain sight, but not exactly hidden.
Trubel tells the FBI the wessen-free version of what happened and it matches up with the crime scene so she's cleared. Nick and Hank find the octopus guy driving in a dead man's car, but he claims it was borrowed. And since Nick can't see wessen anymore, they have Trubel pretend she's trying to mug him get him to woge and confirm he's the guy they're after. But don't worry, she wears sunglasses so he won't know she's a Grimm.
Munroe and Rosalee show up to help, instead of going on their honeymoon because they're good friends and still the best characters on the show.
The first episode ends with Trubel trailing the octopus wessen, Rosalee and Munroe working to figure out how to restore Nick's Grimm mojo, and Renard flat lining just as a mysterious woman shows up outside his hospital room.
The second episode/part picks up right from there. The woman enters the room, freezes time, and performs some kind of blood/life-force transfusion using a two-headed snake (one head on each end) that then turns to ash on the ground. This works and Renard is alive and the woman turns out to be his mom that looks younger than him (this is actually addressed in-show later). He catches her up on what's been going on, including that she's now a grandmother, but we don't see what happens after she asks when she can see the baby.
Trubel follows the bad guy wessen to a hotel and reports back to Nick and Hank. After getting some money to buy a couple sandwiches for her stakeout right outside his hotel room door. His whole scheme is to steal some top secret info about some national security something or other. The details don't really matter, just that he's a bad guy who needs stopping but there's no normal people evidence of his crimes.
Nick and Hank do some regular police work and find out what he's up to, while Juliet visits Munroe and Rosalee to tell them maybe don't work so hard on curing Nick because now he can just be normal, but they're not sure he can because even if he doesn't have Grimm vision, he already know what's out there so it's more like suddenly having a blind spot (that's my analogy, not theirs) than being free.
The wessen FBI agent woges in front of Nick to see if he's the Grimm and for once he's not so she moves on.
Adalind goes to Victor in Europe because she think he has her baby and she did what he asked and took away Nick's powers. He tricks her into a dungeon and her prison is built just for hexen beasts so she can't escape and he tells her he doesn't have the baby because (as far as he knows) the resistance took her.
Wu finds out Trubel has a police record and starts asking questions about the Grimm book he found, and about Trubel and Hank barely comes up with an excuse to not answer.
Speaking of Trubel, she's followed the wessen to the house of another would-be victim but he ambushes her outside and ties her up. Then he woges but first goes after the other research guy to steal more secrets. While Nick and Hank drive up to the house, having detected where to go, Trubel fights him with both hands tied behind her back (literally, because she has to), and he eventually knocks her down and decides to steal her memories. Bad idea for him and possibly the best moment of the episode.
Octopus Head (the titular character of the episode) ends things with going insane from having seen all of Trubel's memories, a fitting end and a nice way to take out a guy who can't be arrested for his actual crimes.
Wu shows up at Nick's house to ask about the things he's been seeing, but then Nick gets a huge migraine, and it turns out he and Adalind are seeing through each others eyes and hopefully that will motivate her to cure whatever she did because enough with that already. Juliet also asks Nick if he really wants to get re-Grimm'd and he seems to want to
Afterwards, Nick and Hank visit Renard at the hospital and meet his mom, who he says has had some work done. And Trubel gets abducted by the FBI-agent wessen who has figured if Nick isn't the Grimm the she probably is.
One thing I'm wondering: what happened to Nick's extra strength and endurance he got from being turned into a zombie and then cured? Did he lose that when he was robbed of his regular Grimm powers, or did it just gradually go away, or did the writers just forget about it?
What did everyone else who watched (and sees this) think?
ETA: other notes/thoughts
Wu is once again on the verge of learning the truth and being brought into the fold. This needs to happen and soon, it's already been too long.
Adalind isn't alone in the dungeon, there's some mystery prisoner in the next cell. My crazy theory: he's Eric and Sean's secret 3rd brother in a Grimm version of The Man In the Iron Mask. He'd be another bastard child, but one the king is unaware because Victor kept him hidden (he needs comeuppance after being such a dick to Adalind). Other crazy theory: it's the previous king (aka Sean and Eric Renards grandfather) who was overthrown and imprisoned because he was going to make the royal family not a bunch of a-holes and the prince in waiting didn't like that.
Adalind was able to get back her powers (which Nick took away using his blood, so apparently there's a common theme of fluid transfer) after going through some trials, so chances are good that Nick may have to go through something similar. After getting her powers back Adalind seemed to have got them back with some extra power, because she was doing things she never did before, so maybe Nick will also get an extra boost if he gets his powers back (partly to make up for the seeming disappearance of his zombie recovery boost).
I liked in Thanks For The Memories where Nick and Juliet have to clean up all the blood from the beheading. Good to see the real world aspect of all the crap going on.
Trubel seems to be taking the being a Grimm thing pretty well, which is refreshing.