Violette Szabo was born in Paris in 1921. Her mother was French, her father was an English cab driver, and she spent much of her early life in London's Brixton. At the age of 19 she fell in love and married a legionnaire named Etienne. In 1942 her husband was killed whilst fighting the Axis in Africa; in grief, Violette signed up to join the British secret service. Most people spend their early twenties getting wasted and watching bad TV; Violette spent hers parachuting into France, sabotaging the Nazi war effort and helping the resistance. In 1944 she was captured by the Germans, tortured in a concentration camp, and finally executed. She was 23 years old when she died.

Velvet Assassin is a stealth-based action game that takes its inspiration from Violette's story. It's a design decision that has raised eyebrows in certain quarters; some might argue that a video game is not the best place to relate a tale that ends with the execution of a young woman. Let's be clear - this is not Violette Szabo: The Game, but rather an action game whose heroine is based upon a real-life person. Is that any more disrespectful than making anything that allows you to "play" bits of World War 2 - a conflict that ended the lives of over 50 million people?

We hope you will forgive the rather bleak introduction to this preview, as it serves to highlight both the attitude of Velvet Assassin's developers and the rather sombre tone of the game itself. German developer Replay Games says it is creating a WW2 game that does more than simply use the war as a setting, something that actually makes you think a bit about what happened. It's a gamble, certainly - but one that could potentially create something genuinely different from the norm.

The brief half-an-hour preview we were shown at Leipzig was certainly enough to tease out our interest. Our demonstration followed MI6 agent Violette Summer on her mission to infiltrate and destroy a German bunker, a remote fuel depot used to supply German forces. This particular base had its line of communication cut some time ago, and the resulting isolation has eaten away at the mental health of the guards therein.

The action within the level itself played out much as you might expect it to: plenty of sneaking around in the shadows, the stealthy theft of needed items and the occasional take-down of a hapless guard. The latter played out with short bursts of fairly intense violence: stealth kills see Violette plunging her knife into the back of an enemy's head, or via brutal nasty stabs to the back. The animation here is detailed but down-to-earth; executions are far less over-the-top than in games like Tenchu, and they're ultimately more disturbing as a result.

Violette also has the ability to pull pins out of the grenades carried by passing guards; the poor sap just carries on patrolling and explodes a moment later. The unusual thing about these moments is that you might actually feel a bit sorry for the person you just killed. The stir-crazy soldiers in the bunker level were constantly lamenting their miserable state and recounting memories of home, particularly the kinds of food they missed. These details worked largely due to Replay's success in making the bunker seem like a cold, godforsaken place. Trickles of water streaming down the walls gave the level a cold and neglected feel, while the balance of lighting and shadows - vital elements of any stealth game - felt pretty bang on. Violette was also able to pick up and read personal letters left lying around by the guard. Where many games would use these as a means to convey pass codes or other gaming information, here they simply added to the downbeat atmosphere.

Velvet Assassin may encourage you to sympathise with the enemy, but when push comes to shove you'll still have to be ruthless in your efforts to survive. As is typical for these games, approaching guards in direct combat will usually result in death. However, Violette can turn these confrontations in her favour using a special item: morphine. You see, the whole of Velvet Assassin's plot is being narrated via flashback, with Violette recalling the horrors of war from a hospital bed. When the player uses up a hit of morphine, the game shifts into a bright, sepia-tinged alternate reality - it's a bit like the opposite of the Silent Hill effect. During these moments Violette appears to be dressed in just a nightgown, as her past and present merge; more helpfully, these interludes act as a form of bullet-time in which bad guys can be dispatched with ease.

It's a strange concept, one that breaks up the gritty realism with something a lot more fantastical. To be honest, it's hard to tell just yet if it works within the game's wider concept, or whether it's just plain weird. At the end of our test mission, Violette successfully blew up the test bunker, reaching the exit with just seconds to spare. As our young spy reached the door, her surroundings transformed again to those of her hospital ward, time slowing once more to a crawl. Without fully knowing the setup for the full game it's hard to appreciate this moment, but it was oddly poignant, all the same.

World War 2 games are a dime a dozen in this day and age, but Velvet Assassin has a real chance to shake the genre up a bit. The basic sneaking and stealth kill mechanics are looking good, but it's the more unusual touches that could make this game stand out from the crowd. The bleak tone could backfire on Replay, of course. One mission from the final release will require you to help a captured Allied spy. In Medal of Honour you'd be busting your friend out of jail; here you'll be delivering them a cyanide pill, allowing them to off themselves before they're tortured. Some gamers may be put off by such dark objectives, but for now we're happy to applaud a developer who's prepared to take a risk. After all, nothing ventured, nothing gained.