's early 16th century painting,
Mona Lisa, is featured as a major plot point in the film. During the
COVID-19 pandemic in May 2020, Miles Bron, the co-founder of technology company Alpha, hosts a
murder mystery game at the Glass Onion, his mansion on a
private island in
Greece. He sends invitations via intricate
puzzle boxes to his friend group, the "Disruptors": Alpha head scientist Lionel Toussaint,
Connecticut governor Claire Debella, controversial model-turned-fashion designer Birdie Jay,
men's rights streamer Duke Cody, and ousted Alpha co-founder Cassandra "Andi" Brand, who is estranged from the rest. The Disruptors travel to Miles's island, along with Birdie's assistant Peg and Duke's girlfriend Whiskey. Famous detective Benoit Blanc joins them, claiming Miles invited him; however, upon arrival Miles privately tells Blanc that another guest probably invited him as a joke, and lets him stay. Before dinner, Miles shows off his glass sculpture collection and the
Mona Lisa, which he has on loan from the
Louvre. Miles also reveals that the mansion is powered by "Klear", a hydrogen-based
alternative fuel that Alpha will soon sell despite Lionel and Claire's knowledge that it is dangerously volatile. Blanc solves Miles's murder mystery game immediately and privately warns Miles that the Disruptors all have motives to kill him. After an argument with the rest of the group, Andi storms off. Duke suddenly dies after drinking from Miles's glass and the panicked group suspects that Andi attempted to poison Miles. Lionel calls the police but they are unable to arrive until morning. After the group discovers Duke's pistol is missing, a
power outage occurs, prompting the group to scatter. Blanc finds Andi, whom he addresses as Helen, but an unseen assailant shoots her. Blanc gathers the group away from the body and announces that he has solved Andi's murder. An extended flashback shows that Andi had actually died a week earlier, apparently by suicide, and her twin sister Helen hired Blanc to investigate. Andi had halted Alpha's development of Klear because of safety concerns, so Miles fired her. Andi sued Miles, but lost after the other Disruptors
perjured themselves by testifying that Miles and not Andi had single-handedly sketched out the original plan for Alpha on a napkin. Shortly before her death, Andi had emailed the group a photo showing that she had found the original napkin. Helen suspected that one of the Disruptors killed Andi and stole the napkin to protect Miles and themselves. With Andi's death not yet public knowledge, Blanc persuaded Helen to pose as Andi at Miles's party and help him investigate. Helen helped Blanc discover the Disruptors' motives to protect Miles: Lionel and Claire have staked their reputations on Klear, Birdie needs Miles's financial assistance to handle the fallout of ignorantly employing
sweatshops, and Duke was hoping for a show on Alpha News. Each of them visited Andi's home on the day she died. On the island, Helen searched the guests' rooms but did not find the napkin. When she was shot, Andi's journal in her jacket pocket stopped the bullet; with the other Disruptors believing her dead, she searched Miles's office. Blanc announces that Miles committed both murders, having only dismissed the idea earlier because he overestimated Miles' intelligence. Miles drugged Andi and staged her “suicide” after learning she had the napkin, but Duke saw him leaving Andi's house. During the party, Duke saw a news report of Andi's death and, realizing that Miles was responsible, attempted to blackmail him. Miles then poisoned Duke with pineapple juice, which Duke was
deathly allergic to, took Duke's pistol, and shot Helen. Helen locates Andi's napkin in Miles's office and reveals her identity to the group. Miles burns the napkin, eliminating the evidence, and his friends refuse to testify against him. Blanc tells Helen that he has done all he can and goes outside. In a rage, Helen smashes Miles's glass sculptures, and the group briefly joins in. Helen lights a bonfire and throws a piece of Klear into the fire, causing an explosion that destroys the mansion and the
Mona Lisa. With Klear now proven dangerous and Miles's reputation ruined by the destruction of the
Mona Lisa, Miles has no leverage and the group decides to testify against him. On the beach, Helen and Blanc watch as police boats arrive. ==Cast==