Consequences are a big deal in Vampyr, just as they were in Dontnod’s previous game, Life Is Strange. But where once there was teen high-school angst, now the First World War has barely finished and the city of London is experiencing one of the worst pandemics in human history, the Spanish Flu of 1918. And there’s another disease wreaking havoc through the streets of London, one that has conveniently enough turned protagonist Jonathan Reid into a vampire. As the player, that means you’ll need to feed to stay alive. However, picking who to feed on in a city already beset by sickness will leave its mark on the various communities and factions of London.

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“This is the golden rule: you can take the life of everybody in the game, there is no exception, even if it is your own family,” explains narrative director Stéphane Beauverger. “The second important rule is that there are always consequences, there is no free kill. So each time you kill someone, even of a very small level, you will impact the life of people who knew the victim.”

Taking out a thug could save the life of someone he intended to murder, but it will also have an impact on the thug’s son. Players can immerse themselves in that community in order to determine the rippling effect of each of their kills, or they can blindly feed on whoever takes their fancy.

“That’s just the small level, just the family and the relatives of the victim, but at every second of the game there is a dynamic based on the average health of each district of London – if you kill too many people, if you take just one life, of someone who doesn’t seem important or who has no family or no relatives at all, the health condition will go below the critical status and you will lose the entire district.” And when you lose a district, you lose everyone in it: “even the people who were very healthy and you were not aiming to kill, they will be turned into creatures because you went one step too far. There are always consequences.”

With no healthy citizens present the district ceases to be a potential hunting ground for the player, and staying stocked up on fresh human blood becomes that little bit more difficult.

Far from being a playground for the player to abuse and push to its limits, London is the player’s lifeline – they’ll need it for far more than mere survival, says art director Grégory Szucs. “One of the first questions we ask is ‘what have I become? Who did this to me?’ And as a doctor who sees disease you try to cure it and what is happening in London. The hero will always try and have a scientific approach to the vampires: he truly believes this is some kind of disease, but he has no clue so he has first to understand who did this to him, why, what it is to be a vampire, and why all of these vampires have suddenly appeared across London”

Infusing London with all the expected gloom and gaslit horror of a city that’s emerged from four years of war to find itself stalked by nightmarish creatures and teeming with disease was the job of Unreal Engine 4 and its superb lighting tools, explained Dontnod when we last spoke. “Lights, shadows, unsettling silhouettes and an ever-present and suffocating fog are major players in Vampyr, creating an aura of doubt and uncertainty, they are as important as the city of London itself.”

Playing as one of the monsters puts an interesting slant on Vampyr’s moral compass: your enemies are vampire hunters – ostensibly on the side of ‘right’ – your victims are often innocents, and you yourself are a doctor, someone sworn to help others. There are no ‘good guy’ or ‘bad guy’ points for choosing one action over another, but certain aspects of the game might get more challenging or arduous the deeper you venture down one moral path.

Alternatively, it’s possible to complete Vampyr without killing a single human, reveals Beauverger. “You can finish the game without killing anyone, you can feed on the rats if you want: you will get no experience points, you will just get blood. You will stay very weak but you can to do that.” Likewise, enemies can be swayed if you’re able to convince them of your good intentions: “you are not a real hero, the real heroes are the vampire hunters who try to take you down. You have to deal with the fact that you are a beast and an evil monster and you will have to prove to them through your actions that you can be trusted and are not someone who is completely heartless.”

On paper, Vampyr is drastic departure from the carefully trod tone and grounded dilemmas of Life is Strange. Pandemic-stricken London might be your hunting ground, but it’s one that’s fraught with consequences – good and bad – depending on how you play it. Doctor Jonathan Reid is still a rational man who wants to do good, but deciding how to handle his monstrous side is what Vampyre is all about.

Vampyr is due out on PC in 2017. Unreal Engine 4 is now free.

In this sponsored series, we’re looking at how game developers are taking advantage of Unreal Engine 4 to create a new generation of PC games. With thanks to Epic Games and Dontnod Entertainment.