The Moss Harbor Bridge Group, a club of adult card players, meets weekly to play Bridge. During one game, Mattie Whalen’s partner, Olivia Korhonen, mouths to her, “I will kill you.” Olivia joined the club a few weeks earlier and seemed normal and pleasant. The game then ends badly, and Olivia reassures Mattie they’ll win next time. However, as she walks away, Olivia mouths again, “I will kill you.” Mattie’s husband, Don, simply tells Mattie they take the game too seriously. The following week, Mattie runs into Olivia at the salon, where Olivia whispers, “I will kill you” again. After that encounter, Mattie contacts her friend Pat Gallagher to receive some advice. Pat’s partner, Babs, says she needs to report Olivia to the police, but Pat says they wouldn’t believe her without evidence. When Mattie parks at home later that day, she sees Olivia wave cheerfully from her car as she turns a corner.       The next morning, Mattie calls Olivia and asks to practice playing Bridge together. They meet at Olivia’s condo, where Mattie tells Olivia she knows she is stalking her and hears Olivia’s words every time they meet. Olivia laughs and tells Mattie to be sure that she will kill her, just not yet. She begins to talk about sheepherding in Finland. She says that family dogs often kill sheep, not out of hunger but simply “killing blindly.” She says that the passivity and stupidity of the sheep trigger the dogs into a killing frenzy. Olivia tells Mattie that she is her sheep, then asks her to leave her, saying she has guests arriving soon.      At dinner, Don dismisses Mattie's claims again, calling it “middle-school bullshit.” Mattie says out loud that he’s right, that Olivia won’t kill her, and likes the sound of it. At the next Bridge game, Mattie purposely plays poorly. Olivia mouths the words again, but Mattie immediately chides her and says they must not signal each other. After the game, Olivia tells Mattie she is being childish and spoiling the game. Pat and Babs tell Mattie to keep surprising Olivia but to be alert because she had probably killed before.       For several nights, Mattie parks across from Olivia’s condo to watch her. Olivia comes out of the apartment one night and walks straight toward Mattie’s car, telling Mattie to walk with her. They go to the nearby beach and stand by the water. Olivia tells Mattie that she’s changed and she will be a little sorry to kill her. Mattie senses the upcoming fight and hits Olivia hard in the stomach. They wrestle, and Olivia drags Mattie toward the water’s edge. However, Mattie successfully holds Olivia’s head under the water, then takes the keys from her body.       Mattie drives to Olivia’s condo, where she finds a hidden room with countless candid photos of women and some men. Mattie finds a picture of herself on the wall with a scarf she had lost thumb tacked under it. Mattie analyzes the other photos, each having an associated memento attached to them. Mattie feels confident that the police will find the body and the room of photos. She leaves the apartment door open, and heads home, feeling strangely invulnerable.