Despite the spoilers that leak online from its British run, the period drama has been a ratings hit for public TV, PBS chief executive Paula Kerger told the Television Critics Association on Tuesday.
"You kind of don't want to mess with that if it's working so well," Kerger said.
Word-of-mouth from the British airing helps create buzz and promotion in advance of its PBS run, she said.
The show begins its fourth season in Britain this fall, with PBS airing it starting Jan. 5. It picks up after last season's death of scion Matthew (Dan Stevens), heir to the English estate at the drama's center. Newcomers include Paul Giamatti as an American relation.