This Is Us Star Chris Sullivan Promises 'Completely Unexpected' Season 4

This Is Us returns for season 4 on Sept. 24 on NBC

This Is Us’ fourth season is nearly here, and it seems there will be more twists and turns than ever before.

Chris Sullivan, who plays Toby Damon on the NBC hit series, told PEOPLE Now on Tuesday that the upcoming season 4 will be anything but predictable for fans.

“The places where this season goes, I think they’ve said it all … it is completely unexpected,” said Sullivan, 39.

“Wherever you think we are going, we are going in a completely different direction,” he added. “The way the stories are unfolding is pretty amazing. Our writers and Dan Fogelman have done a pretty amazing job over four seasons keeping people surprised.”

Throughout season 3, Toby struggled with his anxiety and depression as he and wife Kate (Chrissy Metz) awaited news of her pregnancy. During the pregnancy, Toby had a breakdown, which Sullivan recalls as his most “intense” scene he’s done on the series thus far.

Ron Batzdorff/NBC

“On that day, we were shooting two different crews, so the people who normally shoot with us were gone,” he explained to PEOPLE Now. “So it was a cameraman I had never met, a sound guy I had never met.”

“It hurts,” the actor noted of the change in production at the time, recalling, “It was like being surrounded by strangers, like alright, well there goes the kind of comfort level or the safety factor.”

The conclusion of the third season gave a peak into the future for the Pearson family, which showed most of the clan, Toby included, visiting an ailing Rebecca (Mandy Moore). In the present, Toby and Kate welcomed their son Jack, named after Kate’s late father (Milo Ventimiglia).

Last month, This Is Us earned eight total Emmy Award nominations, including Sullivan’s first-ever nomination in the supporting actor category. Moore, Ventimiglia, and Sterling K. Brown also earned nominations for their roles.

While details about the fourth season have been kept under wraps, it was confirmed in June that Once Upon a Time alum Jennifer Morrison would be joining the cast in a “substantial” recurring role.

Maarten de Boer/NBC/NBCU Photo Bank via Getty Images; JB Lacroix/Getty Images

In May, NBC announced that it had renewed This Is Us for an additional three seasons, taking the show through its sixth and likely final season in 2022.

“We’re roughly in the middle of where the television series is going to go,” Fogelman told The Hollywood Reporter ahead of season 3’s finale and ahead of the show’s renewal. “We never set out to make a television series that was going to last 18 seasons, and so we have a very direct plan. I have script pages I have written, and I’m writing that really deep, deep, deep into the future. We have a plan for what we’re going to do, and I know what the plan is.”

Ventimiglia, 41, shared in May that he knows how the series will end — and said it’s going to be “amazing.”

“By the time we get there, it is going to morph into something that we could not dream or imagine it could become,” he added, also sharing his appreciation for the team behind the show. “It’s a lovely machine of artists, and I’m grateful.”

This Is Us returns Sept. 24 at 9 p.m. ET on NBC.