When creator Dan Fogelman first pitched NBC on the arc of “This Is Us,” he promised that every episode would have a watercooler moment that would have people talking the next day.

Recalls Jennifer Salke, NBC’s president of entertainment, “He did say that over the course of time, he would always have those big moments and those big hooks and surprises and reveals, but that they wouldn’t have to be every week because once you’re invested in these characters, a smaller moment could feel as big as those huge moments once you’re totally engrossed in the stories of these characters’ lives and the decisions that they make.”

But no one moment would feel as big as the reveal that the main character, Jack, was dead in the present day. That twist would wind throughout the entire first season, with Fogelman doling out clues like breadcrumbs as to Jack’s ultimate fate. (Who could forget the reveal of the urn in Kate’s living room?)

But the ultimate cause and timing of his death? Viewers are just going have to be patient, he says. He has a plan for answering the question, but it’s not going to come in the March 14 season finale.

“By the time we get to the end of the season, we’ll have done everything exactly as we set out to do,” he tells Variety. “Very few details changed from my initial plan. The second season is going to play out much the same way. Whether we’re going to be able to continue doing that without the audience ever becoming frustrated — that’s going to be one of our biggest challenges.”

But careful watching will be rewarded, he promises. “I describe it a little like pieces of information flying over the air and we let the audience grab them,” he says. “They’re slowly getting the shape of this big event in the family. Did it happen when the kids were in their 30s? Did it happen when the kids were younger? How did it happen? Was it sudden? Was it slow? We’ll get a lot of that information, but the real story of it will play out not in the near, near future. In terms of seeing the moment where something happened to Jack, that’s a little ways away. Where it will be finally all fully revealed, that’s a ways off.”

But what the audience doesn’t know, the cast does — especially Mandy Moore (Rebecca). “Mandy needs to know that,” he explains. “She’s playing an older version of herself. She needs to know when she lost her husband and how it happened.”

It will be “heartbreaking,” promises Moore. “What else can you expect from this show? Heartbreaking in the way that life is heartbreaking. That’s what I love about this show. The way he passes away is going to be heartbreaking for people.”

All the online speculation about Jack’s death, especially the fan fiction, has caught Fogelman by surprise, he admits. “I was expecting it would affect people,” he says. “I just wasn’t expecting the scope of the conversation would get this big.”

WATCH: ‘This Is Us’ Cast on How They Reacted to Jack’s Death