The movie enters a surreal world where time is currency and everyone's life freezes at the age of 25, at which point they begin counting down to death and must earn "time" to stave off the inevitable. Each character carries a digital stopwatch on his wrist, detailing in exact hours and minutes how much time is left.
Seyfried plays Sylvia Weis, a rich but bored aristocrat who has all the time in the world thanks to her privileged connections. Yet she yearns for adventure and Justin Timberlake's character, an instinctive type of guy from the wrong side of town, provides her with exactly that when he kidnaps her and opens her eyes to how the other side live.
Seyfried admits the plot is "ridiculous at times" and "far-fetched" but nevertheless was drawn to the script because of its "grounded, relevant" themes of the gap between rich and poor, and pervasive social injustice.
I literally flew underneath Justin, he landed on top of me
For one of Hollywood's major emerging talents, Seyfried is surprisingly relaxed and easy-going when we meet at The Savoy Hotel in London to talk through the film. Petite with long blonde hair and enormous eyes, it's easy to see why she works well on-screen - but it's her versatility rather than her looks that has made her major business in Hollywood over the past few years.
Though acting since a teenager, it was not until her lead in 2008's Mamma Mia! that Seyfried was recognised as hot property. In Time is just one of five films she's signed up to over the next two years - but it's one she clearly believes in, particularly relishing the dramatic redhead makeover her role brought.
"I had no idea that I was going to be able to look that way – it was a big departure from the way I normally look ," she says. "I think people have a hard time wanting to change that look because people that do know me have gotten used to this. It was nice to have a really stylish, futuristic look as well … we had to fight for that wig though. They just wanted to keep it blonde and we even it tried short blonde but it just didn’t work. It needed to be that kind of red."
We had to fight for that wig. They just wanted to keep it blonde
Alongside the wig, Seyfried also had to contend with six-inch heels - all the while in full gun-toting, car-chasing action movie mode.
"Louis Vuitton boots and YSL pumps… oh god, It was awful," she recalls. "On the second day I was running and I didn’t have the stunt heels on yet and I fell so bad … luckily I was holding onto Justin’s hand so he had to swing me down without hitting my head – really funny but really scary at the same time. I literally flew underneath him, he landed on top of me like this (gestures). It was just because I was running SO fast, the fastest I could ever possibly run with heels bigger than these on – god, terrifying."
Despite the running in heels challenge, Seyfried clearly enjoyed her stint as an action hero and "being one of the dudes," as she puts it.
"I think I even hit my head at one of the crash scenes when Raymond Leon’s (the token bad guy) car crashes into us near the end and I whacked it – and I felt like a dude… I loved it. They didn’t treat me any different because I was a female," she says.
But even with all the excitement, Seyfried's not willing to embrace action full-time, at least for now: "I just don't think I’ll ever be like Angelina Jolie in that respect because it’s just so full-on, you get really tired really easily."
I liked Boyz II Men, I went to their concerts. I was obsessed
Another concept she's keen to dispel is that she used to own posters of co-star Timberlake. "I don’t think I ever had posters of him," she begins, uncertainly. "I still have this old phone from my bedroom in my childhood home and it has like these stickers from Cosmo girl, and you know you get these stickers out of magazines... I just liked every boy, I liked every boy band. I liked Boyz II Men, I went to their concerts. I was obsessed, it was crazy – singing and dancing, it was hilarious."
And that's the charm of Seyfried. She's not afraid to make fun of herself and talk about random, goofy stuff like her childhood crushes.
Whether or not JT is one of them remains to be seen, but Seyfried does admit that working with him was "amazing."
"He's really hard-working, really professional but just a lot of fun," she says. "It was quite a lot of laughs, which is so important because you need that ease between takes in order for the chemistry to be right. You have to really respect each other and enjoy each others’ company."
So with In Time wrapped and two more movies in the pipeline, how is a life of fame and fortune panning out?
"It’s really stressful, some of the aspects of it," Seyfried says. "(But) I have to say, I’m enjoying myself so much, I have so many opportunities to travel. I have money, I can support people if I wanted to, if I needed to. I’m not scared right now."
With Hollywood at her beck and call, we're not surprised.
In Time is out in cinemas nationwide now