Supernatural drama “Manifest” was the unexpected hit of last year’s TV season, premiering on NBC to over 10 million viewers in an era where half that number is considered a win.

Now in its second season (Mondays at 10 p.m.), the series follows a group of passengers aboard an airplane who, upon landing, discover that five years have mysteriously passed while they were in the air. They were presumed dead and their loved ones moved on, and things grew even more complicated when it became apparent their ordeal gave them supernatural abilities — including visions they refer to as “callings.”

“When anything is a hit, it’s always a surprise,” says series star Josh Dallas, 41, who spent seven seasons on ABC’s “Once Upon a Time” before joining “Manifest.” “I don’t think anybody knows what makes a show connect. But I’m just incredibly lucky and grateful that I’ve been part of two shows now that seem to have taken people on this ride.”

Dallas, who plays Ben Stone — an associate professor who was on the plane with his son Cal (Jack Messina, “The Marvelous Mrs. Maisel”) and his sister Michaela (Melissa Roxburgh, “Supernatural”) — sees a correlation between “Manifest” and his former series.

“There is a similarity between the two [shows],” says Dallas, who met his wife Ginnifer Goodwin while co-starring with her on “Once Upon a Time.” “I’m interested in stories that have a big idea and a big concept but also have something very grounded about them. ‘Once’ was this wild idea but it was … about this family and these people trying to find out where their place is in the world.

“In many ways, ‘Manifest’ mirrors that,” he says. “The idea of a family trying to find their way back to each other is something that I really like. That’s a universal kind of theme.”

Complicating things for Ben is that his wife, Grace (Athena Karkanis, “House of Cards”), mourned him and moved on while the plane was missing. Season 1 ended with the news that she’s pregnant, but the baby might not be his. Season 2 will see their relationship in a more stable place, Dallas says.

“Their relationship is a bond that becomes stronger throughout Season 2. I feel if Grace and Ben are together, there’s a bit of hope in the story of the passengers. So I think they’re going to come together in such a strong way … that it’s going to help Ben push forward and fight for his family even harder.”

In Season 1, the “Manifest” passengers also made an ominous discovery: they have a looming date of when they’ll all die: June 2, 2024, five years after their missing flight returned. Dallas says that will be a major factor going forward.

“Season 2 is packed full of so many exciting things,” he says. “As far as Ben is concerned, he finds himself in this role of guardian or caretaker of the passengers. This season sees him go down this rabbit hole of trying to find a loophole in this looming death date. So he is on this journey to find a way to hopefully stop that.

“But at the same time, we have old enemies, and a bunch of new enemies, who are making every day a struggle to survive,” he says. “There’s a lot happening; we’re going to get more answers and a lot more questions.”

Because “Manifest” is filmed in Long Island City (Queens) and Manhattan, Dallas, who lives in LA with Goodwin and their two sons, says this is the longest amount of time he’s ever spent in New York — and he’s taken advantage of it.

“I go to the theater as much as I possibly can,” he says. “The last thing I saw was ‘Slave Play’ which is extraordinary. Before that, I saw ‘The Girl From the North Country,’ the Bob Dylan musical, which I loved. [The theater] is the world’s best — if you’re here, you’ve got to take advantage of it.”