They're calling it a cross between North by Northwest and The 39 Steps. U.K.-based indie outfit Six to Start has taken to developing a new modern conspiracy story for mobile, penned by author Naomi Alderman (probably better known in gaming circles for her scriptwork on the studio's main project Zombies, Run!) And like its Run!, The Walk continues the studio's experiment in merging an extensive narrative with the typically dry fitness gaming genre.

'Nobody else is talking about doing narrative fitness games...'

The Walk, which is slated to launch on mobile devices later this year, is a slight departure from Six to Start's earlier fitness project. Part of that difference is obvious from the name. Unlike Zombies, Run!, The Walk encourages its players to walk — not run — while accompanied by a storyline that is part euro-techno thriller and part a case of mistaken identity.

You're given a vital package that needs to be couriered to Edinburgh, Scotland. You're about to get on the train when terrorists, attempting to get hold of this thing you have, blow up the station. An electromagnetic pulse kills all things electronic — cars no longer work. Now you're forced to walk the distance with the police on your tail.

"Nobody else is talking about doing narrative fitness games," Naomi Alderman told Polygon. "The whole genre is just about gamification now."

'The people who talk to writers less than the tech people are the sports people.'

"One thing that we frequently talk about here is that the issue is down to there not being that many novelists who are friends with people who run games companies. And there are not many games companies that are friends with people who write novels. Part of that problem is that people who are interested in story and people interested in technology are put into different educational buildings from the time they're about 15 years old, so those people just don't talk to each other and I think that's a general problem with stories in games. Even moreso when you talk about jocks, the people who talk to writers less than the tech people are the sports people."

Despite the fitness genre being populated by more traditionally-styled and story-less gameplay, the team of Six to Start are skeptical of the success of this method.

"There are companies out there who team up with well-known health professionals and make these games, and they just don't seem to work," said Alderman. "People who are focused on health and sports see these games as something that needs to take on a competitive structure. They introduce these success ladders in those dancing games, which is something that would exist if you were competing in the actual sport. For those of us who aren't professional sports people, who have no ambitions in that area, it's hard to work out why we're forced to compete like that."

'There are companies out there who team up with well-known health professionals and they just don't seem to work...'

The Walk is being created with the help of the National Health Service in the U.K. as part of an initiative to encourage the public to walk regularly. Not only is it designed to function as a pedometer and game combined, it will reward players for not being sedentary using in-game rewards.

"We thought a lot about how to conceptualize that being active is not just a one-off activity," said Alderman. "It's something that every bit of incremental effort works towards, and we thought about this idea of a really long journey. It's not unlike Lord of the Rings perhaps, there's a little bit of walking to Rivendell, Fellowship perhaps."

'It's not unlike Lord of the Rings perhaps...'

"Getting into the habit of moving more is a big process," said studio co-founder Adrian Hon. "It can take several months to get in the habit, so the idea of having a single, huge, long journey is just more inspiring than short or intense exercises. We're sensible about this. The only way you can get up to what health officials say you should be walking, which is about 10,000 steps per day, is by walking throughout the day. It's by taking a 10 minute walk, going to the shops, small stuff like that.

"We're trying to get people to walk throughout the day, that's why we're doing this with the NHS. It's going to be the best pedometer you've ever had but it's also got a game built into it. So you're kind of playing all the time whenever you have your phone with you."

'Emotions are often heightened by exercise...'

The tech behind The Walk differs from what the studio introduced in Zombies, Run! — a game that took it on faith that you were exercising. In The Walk this system would be too open to abuse. Instead the game checks in with you throughout the day, samples your movements and works out what activities you're doing to work out a picture of your day. The result is an estimate of how much walking you've done.

But beyond using story to egg the player on and keep them active, Alderman says that exercise actually helps to heighten emotions throughout the narrative.

"Emotions are often heightened by exercise," she said, "and certainly I've had that experience a few years ago when I was grieving for a family member and I found that every time I went to the gym at the end of the work out I would start crying. As if, I don't know, the hormonal release or something brought it all to the surface. I think that helps the story. We are piggy-backing off the running hormones and it makes everything feel much more intense."