A breakup is coming.

Sophie Turner accidentally played a part in a celebrity couple breaking off their engagement after a San Diego Comic-Con afterparty run-in years ago.

The actress, 29, explained to Seth Meyers on Thursday that her “quite crazy” evening “went really south really quick” when her childhood friend asked for a favor.

“She saw this actor she, like, loved,” the “Game of Thrones” alum explained on “Late Night With Seth Meyers.”

When Turner’s pal begged her to “say hi,” she simply waved at the man from afar.

“That was it,” the Emmy nominee insisted. “Later on, I see this girl looking at me and she’s a famous actress. And I go, ‘I have to go and tell her how much she means to me.’”

Turner “dance[d] on over” to the woman — only for the unidentified A-lister to ask, “Can you stop f–king flirting with my fiancé?”

When Turner asked who the woman’s partner was, she “point[ed] at the guy” the “Joan” star had waved at.

“I have no idea who this man is,” Turner claimed. “Turns out, they broke their engagement off that night because of my [wave]. I didn’t realize I held this power.”

Turner noted that she couldn’t reveal the couple’s names or she would get “in trouble.”

Elsewhere in the interview, the “Staircase” star spoke about how “vile” it was to kiss her former onscreen sibling Kit Harington in their upcoming movie, “The Dreadful.”

She confirmed that her intimate scenes with the 38-year-old were “worse” than filming with cockroaches and a mouse in her latest release, “Trust.”

“We get on set and we are both retching,” Turner recalled of the “really bad moment in [her] career.”

As for her offscreen love life, the “Dark Phoenix” star has been dating aristocrat Peregrine “Perry” Pearson on and off since 2023 following her divorce from Joe Jonas.

She and the Jonas Brothers member, 36, co-parent daughters Willa, 5, and Delphine, 3.