All it took was one look at the script, and Jake Gyllenhaal wanted in on “Source Code.”

Gyllenhaal was intrigued by Ben Ripley’s science-fiction thriller about a soldier in a high-tech project, the Source Code, which sends him back in time for eight minutes so he can change events.

“The first 15 pages that I read are like, the first five minutes of the movie,” Gyllenhaal said last Sunday at the Four Seasons Hotel in Los Angeles.

“You’re like, ‘What the hell is going on?’ I thought that they couldn’t take it any farther than it had already been taken.”

Instead, “It just got better and better, more tense and more engaging.”

To make “Source Code,” Gyllenhaal knew one person (besides himself) was key.

“I knew the only way that this is going to work is if we have a director who understands that it’s about the dilemma of this character and what the character is going through,” not the sci-fi premise.

That guy is Duncan Jones, David Bowie’s son.

Perhaps Gyllenhaal’s gut feeling about the “Source Code” script can be chalked up to maturity — the actor who played the troubled teen in 2001’s “Donnie Darko” is now 30 years old.

“I feel like I’m lucky to have gotten to 30. There’s a great confidence that comes with it, a real security in understanding myself,” he said.

“This movie is actually a nice representation of that, because there’s a lot of trusting my instinct, trusting that I love this story and that I was going to go with it and never second-guessing it.”

Gyllenhaal hopes moviegoers will respond to his love story with Michelle Monaghan, set on a speeding train bound for destruction.

“In the end, it’s romantic. The choice for this guy is not like, ‘Oh, am I really going to save the world?’ The choice is that he starts as a guy essentially in someone else’s body who is nervous to ask this girl to get a cup of coffee and then has to get blown up eight times to realize that maybe he’s got to ask this girl out for a cup of coffee. So I do relate to that.

“Sometimes it feels like when you walk up to somebody and you’re intrigued by them, to gather up the gumption, to ask someone a question like that, feels like you’re blowing up inside eight times.”