Spoilers follow.
In Ocean's Eight, Debbie Ocean's crew steals the $150 million Toussaint necklace from Daphne Kluger at the Met Gala, frames Claude Becker, and secretly swaps the museum's royal jewels for fakes. The plot is easiest to follow as a sequence of steps, so that is how it is laid out here.
Step one, the target. Debbie Ocean walks out of prison and starts the job immediately. The prize is the Toussaint, a Cartier diamond necklace worth about $150 million, which will be worn at the Met Gala.
Step two, the crew. She brings in her old partner Lou, then builds the team: designer Rose Weil, jeweler Amita, hacker Nine Ball, pickpocket Constance and fence Tammy.
Step three, the delivery. Rose becomes the stylist for Daphne Kluger, the gala host, so that Daphne is the one who wears the necklace. Amita and Rose make a convincing replica, Tammy takes a job at Vogue, and Lou attends the gala in disguise to help from inside.
Step four, the night. Daphne is slipped something in her soup and leaves the room, which lets Constance lift the necklace. Amita breaks it into pieces that the crew smuggles out of the museum, and the replica is left behind so that nothing looks wrong.
Step five, the fall guy. Debbie also sets up Claude Becker, her former partner and ex-lover, to take the blame.
Step six, the complication. Daphne works out what happened and agrees to join the crew as the eighth member in return for a share. With Debbie, Lou, Rose, Amita, Nine Ball, Constance, Tammy and Daphne, the crew reaches eight. Insurance investigator John Frazier suspects Debbie, but her alibi holds up, and Becker is arrested once the stolen stones have been sold.
Step seven, the second theft. It then emerges that Lou and Yen also stole royal jewels on loan to the museum during the lockdown and swapped them for Amita's fakes, a haul worth more than the necklace. The crew splits up to enjoy their money and start new ventures, and Debbie visits Danny's grave and raises a martini to him.