Bucky shifts into Russian without even thinking about it as he demands of Natasha, "ты с ума сошёл?"

"Успоко́йтесь, всё бу́дет хорошо́," Natasha flashes back. "ты знаешь, что она хороша. вы тренировали ее."

"Не в э́том де́ло!" Bucky argues, at which point Natasha rolls her eyes and looks past him at Steve.

"She's my sister," she says. "James is being overprotective."