You can read our full ending explainer here, but ultimately, the killer turns out to be billionaire tech bro, Miles Bron (Edward Norton).
"Glass Onion" picks up a few years after "Knives Out," with Benoit Blanc (Daniel Craig) contemplating life at home during lockdown when a surprising case comes out of the blue. It's not long before the detective is whisked away to a Greek island owned by Miles.
But when the entrepreneur's closest friends arrive on the island, it quickly becomes apparent that there's some bad blood between them all, in one way or another. It all stems from the fact that Miles swindled Cassandra "Andi" Brand (Janelle Monáe) out of their groundbreaking company, Atmos.
To make matters even more intriguing, Miles isn't the one who invited Benoit, and it quickly becomes a race to figure out who's causing the chaos during the fun holiday weekend.
When Duke Cody (Dave Bautista) is mysteriously killed in front of everyone, Andi's twin sister Helen (also played by Janelle Monáe) also gets shot in the middle of a blackout while masquerading as her sister.
Although director Rian Johnson positions Miles as a potential victim of the unknown killer, the end of the film unmasks the billionaire as the one behind it all, as he tries to cover up his own dastardly deeds.
But there are four clear clues early on in the film that point toward the "Glass Onion" ending.