Tanya (Jennifer Coolidge) was always the strongest guess for who died, and it turns out this theory was right. At the end of the fourth episode, she agrees to go on a trip to Palermo with a bunch of gay guys she just met. Conspiracy-minded fans on Twitter speculated that maybe her husband, Greg (Jon Gries), hired them to kill her, and they ended up being right.
In episode five, Quentin (Tom Hollander) takes Tanya to see the opera "Madama Butterfly," which is about a woman who's abandoned by her husband and dies by suicide. Songs from "Madama Butterfly" are used to soundtrack some of the devastating moments from episode six. Tanya attends a party thrown by Quentin. It's very important to Jack (Leo Woodall) that her assistant Portia (Haley Lu Richardson) isn't there. Quentin gives Tanya a ton of cocaine and then has one of his friends seduce her. While Tanya is waiting for her lover, she sees a photo of Quentin and someone else in cowboy hats.
In the final episode, the men take Tanya on the yacht back to the hotel in Taormina. She's unsettled, but she's not fully suspicious until Portia calls her and tells her Jack has basically kidnapped her. Together, they put together the pieces — including the photo of Quentin and a cowboy who looks a lot like Greg — in place and Tanya decides they're trying to kill her so Greg can get her money despite the prenup. Technically, the men never confirm this goal; they could have just been blackmailing her with her infidelity. But once Tanya finds a gun on the boat, she's convinced.
With the gun, she shoots blindly at all the men. At first it seems like her shots are missing their target, but the camera pans out to reveal she hit and killed them all. She tries to climb down to the boat to shore, but hits her head and drowns.