Yellowstone used code words to keep John Dutton's death a secret

Her lips were sealed.

“Yellowstone” is currently airing the second half of season five, which was announced as the final season of the hit ranch drama.

Before the final episodes ended, Kevin Costner left the series amid rumors of an alleged feud with creator and showrunner Taylor Sheridan.

Spoiler alert: In the premiere episode of the second half of season five, “Yellowstone” addresses Costner's exit by killing off his character John Dutton.

Executive producer Christina Alexandra Voros, who directed the episode, told The Hollywood Reporter that code words were used during filming to keep plot development top secret.

“It's so strange to talk about because it was so secret for so long,” she told the outlet.

“We didn’t talk about it being a death. Every time there is a death or other event, we call it an 'arrival,'” she explained. “And we gave John’s character a pseudonym. We called him “Crosby.” We called the opening scene “Beth Discovers Crosby Has Arrived.” It was on the call sheets and the crew asked, “Who is Crosby?” And where is he from?'”

Voros added that after doing some research, she discovered that John Schuyler Crosby was the last governor of Montana before it became a state in the 1880s.

“It was a very random, obscure, esoteric allusion [by Sheridan]” she said.

“Yellowstone” follows the Dutton family, owners of the largest ranch in Montana, including patriarch John (Costner), who had become governor of Montana before his death, and his adult children, the quiet Kayce (Luke Grimes), the villainous Jamie ( Wes Bentley), the headstrong Beth (Kelly Reilly) and Beth's cowboy husband Rip Wheeler (Cole Hauser).

In the premiere episode of the second half of season five, it was revealed that John was fatally shot by a hitman, but this was staged as a suicide.

Beth and Kayce both didn't believe it was suicide, and Beth was sure Jamie did it. She was mostly right, but Jamie's guilt was indirect, as his lover, lawyer Sarah Atwood (Dawn Olivieri), orchestrated it, to Jamie's obvious dismay.

Fans were not happy with how the show handled Costner's exit.

One viewer said: “Even though we knew KEVIN COSTNER wasn't supposed to come back for the rest of #Yellowstone. The way he ended his character was just baffled and lazy. Could have been a better way, or he could have just ridden off into the sunset.”

Another fan complained: “The fans of this show and Kevin Costner (John Dutton) deserve much better!” Taylor Sheridan I don't know if I'll support another one of your shows!!! #Yellowstone and the ratings will suffer! Laziest writing.”

“Yellowstone” airs Sundays (8:00 p.m. EST) on Paramount Network.