If you're a mystery fan, then it's not just the "who" in whodunit that matters to you, it's also the why. And with any good murder mystery, the cast of characters that surrounds the person who ends up dead all have at least one motive that would make them a viable suspect. That is true in Glass Onion: A Knives Out Mystery, Rian Johnson's sequel to Knives Out, but the "who" and "why" are far less interesting than the details of how the truth is revealed.
Tech billionaire Miles Bron (Edward Norton) invites his oldest friends out to his private island to spend the weekend. There, they are supposed to take part in a murder mystery game that would see him fake deceased during the first night's dinner, leaving the rest of them to try to solve the fictional crime by the time they cross his Banksy dock to board a boat home. Only, the very real (in this world) and very famous detective Benoit Blanc (Daniel Craig) infiltrates this weekend (more on that in a minute) and cracks the case before it even opens. Yes, his keen observation skills spy the way the room is laid out, Miles' position at the table, the necklace he wears, and the strategic nostalgic props he laid out in his home that would implicate his long-time friend, supermodel-turned-editor-turned-fashion designer Birdie Jay (Kate Hudson) as having killed him because he stole her diamond.
But the weekend is far from lost. Because the truth is, the minute the guests stepped off that Banksy dock the first time, something was afoot.
Not only was Benoit there, when Miles did not invite him, but so was Miles' ex-partner Andi (Janelle Monáe). But how, when Andi died a week earlier?
Only her killer knows an attempt on her life was made well before the weekend getaway. And, in theory, her killer also knows that who is standing before him is an imposter, aka Andi's twin sister Helen, there to suss out what happened. But the killer has to play it cool until he can find out what her plan is, right?
Well, sort of. Because it turns out the killer, Miles (in a way, who else could it be but Norton?) is not a smart man, let alone a visionary of any kind. But he can recognize someone else's good idea when he hears or sees it. And so, when Benoit tells him he is a very real target because of how much his so-called friends hate being under his thumb — he bankrolls everything they do, from directly employing Lionel Toussaint (Leslie Odom Jr.) to funding Claire Debella's (Kathryn Hahn) political campaign, for example, but that puts them in hist debt — he steals Benoit's metaphor of having a loaded gun in a room in which all the lights go out and makes it a reality. And he shoots Helen.
Only Benoit knows Andi is dead because Helen told him. She visited him at his home when he was lamenting not having anything to get him excited, and she laid out everything — from how her sister met Miles and introduced him to the rest of her friends, to how she came up with a billion-dollar idea that she partnered with Miles on, only for him to end up claiming it was his idea originally. And he got all of their friends to lie under oath about that as well. But Andi found proof that she was the one that started it all, and she emailed the others to tell them so. Lionel, being a loyal employee, shared that information with Miles, so Miles took matters into his own hands and visited Andi at her home, where he drugged her and then propped her up in her car, with the motor running, in her closed garage. Her death was called a suicide, but Helen didn't buy it. Hence why she called upon Benoit to get to the bottom of it.
He convinces her to play the part of her sister, which includes her changing her hair, her voice, and her style of dress, and the two try to gather as much evidence as they can as to who could have done the deed while they are on the island. But news of Andi's death breaks while they are there and influencer Duke (Dave Bautista), who had Google Alerts set up for all of his friends and interests (including "movies"), sees it and shows it to Miles, using it to blackmail him into giving him his dream job. (Duke also saw Miles leaving Andi's house the night she died, and he, smarter than Miles, puts it all together.) So, Duke has to go.
Miles pours pineapple juice into a drink he hands Duke, and Duke's allergy does what even Miles knew it would and takes him out. Interestingly, the film plays with the idea of people (including the audience) being willing to accept what they are told, rather than what they actually see here, as the original shot clearly shows Miles handing Duke a specific drink, but later, when everyone is trying to figure out what happened, Miles says Duke must have picked up his (meaning, Miles') drink by mistake, and the footage shows that. It's not the only time the film plays with perception, nor is it the only comment on how these wealthy men who control everyone get away with their dastardly deeds, but we digress.
Duke's death is a catalyst that sends everyone spinning, but it is also what gives Miles his opportunity. He is able to grab Duke's gun and stash it to use later, when the time is right.
Though, thankfully, things are never truly on his side. Sure, he manages to shoot Helen, but he hits her where she happens to have a leather-bound journal in her pocket, which catches the bullet. She and Benoit then decide to fake her death (using hot sauce to look like blood) in order to buy them more time. She needs to get proof that Miles stole Andi's proof of the business being her idea, which is the original cocktail napkin from the bar they used to frequent, on which she jotted down the notes.
If you think finding it and confronting Miles with it is enough, you don't know Johnson that well. Because it's not just Andi's life he destroyed: His latest business venture, the one that Andi was not supportive of, which caused the split and him to lie about the company's origins in the first place, is to fuel people's homes with hydrogen. Yes, it's cleaner, but it's also not safe. Remember the Hindenburg disaster? Claire sure does.
Miles sets fire to the original napkin, but Helen counters (first by smashing all of his ridiculous glass statues and then) by tossing a little piece of that hydrogen-fuel source into the fire. He has been running his island on it, and in the presence of fire, it does what everyone but Miles knows it will and explodes. No one is severely burned — in fact, both Miles and Helen are able to run through flames to try to reach the Mona Lisa (yes, the real Mona Lisa), which he has on loan. He wants to save it, of course, but she wants to push the security override so that it, too, burns.
If you think that's cruel — depriving the world of a beloved painting — it's just because she knows no one will touch his fuel source when it's the reason the most famous piece of art in the world is now gone. Plus, it's a personal attack on him because of how connected he felt to the painting and how he pretentiously wants to be remembered in the same breath as it. Well, now he will be.
Benoit can't have any part in this. Once he is able to help prove Miles killed Andi, he has to let Helen finish the job, as he is beholden to a set of ethics and the law. He waits outside for the police boats while everything else is going on inside. But through solving the case, he certainly gets his groove back, and he helps one very important woman get answers about, and arguably justice for, her sister.
And Miles? Well, Miles tries one more time to spin the story, but this time his friends turn their back on him. They won't cover for what happened on his island, and they won't even cover for his past misdeeds anymore.