A new fitness app sponsored by the UK Department of Health is a "techno-thriller" that sees a Scottish railway station attacked by terrorists.
The Walk challenges its users to deliver a package from Inverness, the scene of the fictional assault, to another destination in the UK.
Those using the app must walk in the real world to survive in the game and also "save the world".
Health chiefs have said the app could help beat obesity.
Its makers, Naomi Alderman and London-based Six to Start, received a grant to develop the game.
Players are encouraged to walk 10,000 steps every day.
In the game, a bomb explodes at Inverness station and the player's character, Walker, is given a package that could save the world.
Overall, the game takes three months to complete.
Its storyline includes a fictional reintroduction of wolves to the Cairngorms. In real-life, landowner Paul Lister has a long-established plan to release wolves on his Alladale Estate in Sutherland.
Six to Start and Ms Alderman previously designed a smartphone fitness game called Zombies, Run!.
Ms Alderman said: "I'm particularly proud of the immersive world we've created in The Walk - with engaging characters and a gripping story but also a host of maps, newspaper cuttings, audio artefacts and even a comic strip you'll find to help you work out who did plant that bomb in Inverness station, and why.
"The Walk is designed to be addictive, in the best possible way."
The newly-launched app will be included in a research project at King's College Hospital in London.
The study will examine how exercise can help treat patients with rheumatoid arthritis.
Health Minister Lord Howe said the UK government wanted to "encourage innovation" that could help people improve their health.
Other places in Scotland feature in other games.
The name of a Borders town is used for a "druggie hipster" district in Grand Theft Auto V.
Following the release of the game in September, councillor David Paterson said he feared it could "destroy the reputation" of Hawick.
He said a lot of people were "very proud" of the town and it did not deserve such "adverse publicity".
The games series is known for its "tongue-in-cheek" humour and regularly includes Scottish references with the game's maker, Rockstar North, being based in Edinburgh.
A Scottish island has also been twinned with a video game's virtual world.
Skye's twinning with the fictional isles of Skylands was done to promote a new version of Skylanders.
VisitScotland said the move would also boost tourism to Skye, and was the first time a video game "world" had been twinned with a real place.