Full spoilers follow for Stranger Things: Season 5, Vol. 2, which consists of three of Season 5's eight episodes. Vol. 2 premieres December 25 on Netflix and the series finale debuts December 31. Read our review of Vol. 1 here.

Fear not, Stranger Things watchers who are nervous creators Matt and Ross Duffer can’t possibly answer all of their unsolved mysteries – Season 5, Vol. 2 is an answer-palooza for many of the mythology mysteries that have plagued the residents of Hawkins going back to Season 1. There’s so much going on in this trifecta of episodes, it’s a little overwhelming to process just how much is revealed about the mythology – and between characters – in the three-and-a-half hours that span this volume.

And that’s not to mention that you might want to dig out your Texas Instruments scientific calculators, because Mr. Clark (Randy Havens), Dustin (Gaten Matarazzo), Erica (Priah Ferguson) and even Murray (Brett Gelman) will be taking us all to school — in a very entertaining way — as we get the real 411 about the Upside Down, the Rightside Up and something called the exotic matter holding it all together.

"Chapter Five: Shock Jock” is the second episode this season directed by Frank Darabont (The Shawshank Redemption, The Mist) and picks up from the cliffhanger where Noah Schnapp’s Will the Sorcerer went all Eleven on the Demogorgons. In the wake of his destruction, the heroes of Hawkins take stock of their losses… and realize that all 12 kids have been kidnapped into the Upside Down by Mr. Whatsit/Vecna (Jamie Campbell Bower). He’s plugged all of them into his hive, but they just think they’re being protected in his faux-perfect Creel house. Having learned from Holly Wheeler’s (Nell Fisher) wandering, he’s got them locked down for safe-keeping until he needs to use his “perfect vessels” for his endgame plan.

In the Rightside Up, Will and company figure out that he’s able to siphon power from Vecna because of their connection. So, unlike Eleven’s (Millie Bobby Brown) powers, proximity is required for Will to get juiced up to fight Vecna. And Lucas’ (Caleb McLaughlin) theory that November 6 will be the day that Vecna’s plans will become known triggers an implied countdown clock that fuels these episodes, and which unspool over one day. Darabont has a deft hand in keeping “Chapter Five” light on its feet, shifting between multiple settings, some high-concept quantum physics chatter, and several much-needed character moments — hello, Nancy (Natalia Dyer) and Jonathan (Charlie Heaton).

All of that is set-up for the ultimate mythology deep dive in "Chapter Six: Escape from Camazotz," directed by series executive producer Shawn Levy. Consider this the science class episode of the bunch, as Dustin downloads his big wormhole theory that connects Hawkins and Vecna’s The Abyss. All the praise to writer Kate Trefry for packing a tremendous amount of science talk into this segment while parceling it out in ways that make it understandable for all the Steve Harringtons in the house. Does all of it need to be so layered and complex? Probably not, but it’s handed off amongst several characters who excitedly share the details with one another like everyone is stupid (us included). They make the exposition medicine go down easy.

Also tempering the heaviness of those theories is the parallel adventures of Max (Sadie Sink) and Holly working together to get out of Henry’s head (aka Max’s cave). If we’re awarding MVPs for this volume, Fisher’s Holly earns a gold star for being such a charming addition to the lineup so late in the game. She holds her own in every emotional scene with Sink, and does the character work needed to invest the audience in her plight. Not an easy feat when she could have easily come across as stealing precious time from more established characters.

"Chapter Seven: The Bridge" is yet another grand convergence for the cast as all the various factions come back together at WSQK to figure out a plan strong enough to prevent Vecna from merging realities and wiping out their very existence. Everyone plays a part, including minor characters who share in the hero energy like Robin’s girlfriend Vickie (Amybeth McNulty), Mr. Clark, and another feisty turn by Karen Wheeler (Cara Buono).

Vol. 2 absolutely moves the needle when it comes to those all-important who, what, where, and when answers we've been waiting for. Now, we wait for the big one… why?

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Another positive is how Kali/Eight (Linnea Berthelsen) is woven into these last hours in such a satisfying way. It’s like the Duffers recognized how unfair it was that she became synonymous with the most maligned episode of the series — Season 2’s "Chapter Seven: The Lost Sister," — so they’ve given her a gracious do-over. The show’s leaning into her shared history with El means Hopper now has some competition in the familial overprotective department. Kali and Eleven’s sisterly bond is entirely unique to their history, and putting them back together adds a new layer of complications when it comes to the decisions that El makes. They survived an immeasurable level of trauma together in Brenner’s lab, so there’s a lot of weight behind Kali’s argument that it's their duty to prevent it from happening again, even if that interferes with El’s plans for a “happy ending.”

On the checklist of things that don’t work so well, Linda Hamilton’s Dr. Kay is, so far, the Duffers’ least developed of their roster of ‘80s-era actors cast in the series. Don’t get me wrong – Hamilton hasn’t lost her skills when it comes to throwing around dumb underlings, or snarling out orders. But as a well-defined character, Dr. Kay is but a pale shadow of Dr. Brenner. There’s still no context for why she’s all-in about bringing back the number program, which makes her disappointingly one-note. I would have loved to see Hamilton get Paul Reiser-quality material, but that seems unlikely with just two hours left to the series.

Also, this isn’t the best season for Winona Ryder’s Joyce, as she’s strictly been in mom mode. And while that’s important for Will’s character and their bond, it’s limiting for a character who has grown so much up to this point. It’s clear that the romance between Hopper and Joyce — which fueled all of Season 4 — has reverted to best friend mode again. Sure, they’re together, but where’s the love? They don’t need to make out but this season is robbing us of the kind of emotional scenes these two can rip our hearts out with.

Aside from those quibbles, Stranger Things Season 5, Vol. 2 absolutely moves the needle consequentially when it comes to those all-important who, what, where, and when answers to the questions the audience has been waiting for. Now, we wait for the big one… why? As Max reminds us, Vecna started out as a human and there’s still some left in there. Will that be the key to his defeat? If they figure out his secrets, can they bring him back to the light and save Hawkins too?