THIS IS US -- "Vietnam" Episode 305 -- Pictured: Milo Ventimiglia as Jack Pearson -- (Photo by: Ron Batzdorff/NBC) Image Credit: AP

This Is Us series creator Dan Fogelman says the NBC drama’s Vietnam storyline won’t remain a prolonged mystery.

Fogelman says that viewers will know by season’s end how Jack’s younger brother, Nicky, died in the Vietnam War.

The identity of a mystery woman shown with Jack in a wartime photo also will become known this season, he says.

Milo Ventimiglia, who plays Jack, says there will be pain along the way.

The actor says this week’s episode brought him to tears for his character, something he says has never happened before.

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