This Is Us bosses explain the midseason finale twist

Variety

"That was always part of the plan, pretty much since we conceived of the character going to Vietnam and everything," says co-showrunner Isaac Aptaker. "Jack has always been a guy who’s had these secrets and these parts of his life that he can’t talk about, so it always felt to us that there was something big there." Fellow co-showrunner Elizabeth Berger adds: "We loved the idea of figuring out a story where something so complex happens in Vietnam that there was this fractured relationship between brothers, and we look forward to telling that part of the story when we return."

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