I've been writing out the plot to a game, and it's going for a particular message. In order for this message to be conveyed, I need to get the player to commit murder without thinking about it. This much isn't really hard. But what I need most, and where I hit a stumbling block, is making them murder somebody in a time and place where it's clear this is wrong, but I can't actually force them or the message will fall flat. This needs to be avoidable, and all of these murders need to be avoidable, but the player has to fail to realise this the first time through and kill people they shouldn't have. More specifically, the game has the player chasing an assassin who killed their first character (a small boy) and a girl he's with in cold blood. They break a lot of laws along the way, and kill plenty of people who are in their way but don't deserve it. At the end, they finally track down the man's family trying to get them to give up the man's location.

At this point, the player is directed into speaking directly to the man's wife. A lot has happened to make them and their team angry along the way, and this is where I don't really have a plan anymore. I need the player to try and beat the information out of her, and kill her in the process. In front of her children. After this the game shows this scene (followed by every other murder right back to the first) from the eyes of their victims, then shows the murder of those children at the beginning from the killer's perspective. This is made to show how similar their actions were, and the message should be clear.

The issue is I need to make sure the player's conscience doesn't kick in and stop them the first time they play through, but still allow them to avoid all these killings in later playthroughs without changing anything in the game itself, so they can realise that everything they did could have been avoided.

The only similar story I've heard of had the main character remain delusional, he was told to kill civilians by his commander, and then he attempted to get revenge on the commander for being a traitor.

The story used two psychological facts.
First: http://en.wikipedia.org/wiki/Milgram_experiment
Second: Being a fps game, the players automatically believe in taking orders, shooting everyone, and the exciting plot twist of betrayal. That's how they usually work.

I can't really do that. This has to be the player's choice. It isn't about morality and authority, it's about intrinsic assumptions within the medium. I'll get to morality and authority later. (And in greater depth, since that's a subject for which I have plenty of bile to dispense.)

If you can avoid killing, you can only outright trick the people who don't think about it. But here are some ideas to unspolier the game.

• You may present some extrinsic reward system or a walkthrough that doesn't suggest any alternate path, so that players who rely on these things are less likely to find out the plot of the game accidentally.
• You will have to make sure that the player has to work harder to be good, no accidental mercy.
• No accidental killing either right? If you hand them a knife they might stab before they know what's going on like in Calm Time.
• To reduce the severity, you shouldn't actually show the killing until the end, if the player's annoyed enough they'll think about it.

1. There would be a "kills" tally. This would go with no explanation. I'm fairly sure most players will think it's a mark of status at first, but any player who's completed the game will realise this is a mark of shame. Especially since it allows more detail at the end of the game, where you can finally review all your stats, and when reviewed the kill tally gives you more detail. Such as a kill tally of 29 becoming "6 men following orders to protect a man they knew nothing about and wouldn't have helped otherwise, 5 men who never really stopped to consider what they were doing, 4 single men working overtime at a dead-end job they hated, 3 women who couldn't get any other work with their skill set that didn't involve nudity or burger flipping, 3 single fathers whose children are now in a system of constant abuse, 2 newlyweds who couldn't afford a honeymoon with their shitty security jobs, 2 gullible youngsters desperately struggling to believe they're the good guys, 2 security guards wondering if their shift was ever going to end, 1 man who was sympathetic before but sure thinks you're an asshole now and 1 total bastard who actually deserved it." That might be a bit anvilicious, though.

2. Well, they have to think. Less-lethal options are harder to use, and not as effective. (Just like in real life.) Finding a way around takes effort, and sometimes isn't an option. (Just like in real life.) Bribing and conversation are questionable at best and can't always be done, especially if the other side is just as delusional as the typical player. (Just like in real life.)

3. It's going to be pretty hard to kill somebody by accident. You will have whatever weapons you brought, so nobody is giving you weapons at any point, and in conversation they're always put away.

4. Come again?

Ok that's all I have for if you want it to work the first time.

On the other hand, you could alter the allowed perception so players think they're killing monsters. This is would be a lot like accidental killing. I watched a zombie-like movie, where an outtake suggested the virus altered body and perception of the infected to the extent that the "monsters" thought they were super humans and the real humans looked like horribly diseased and dying monsters who kept trying to grab at them.

I can't do that, it'd kill the game's message to overtly alter it like that. At the very least, I can say that people assume they're killing monsters in games anyway, even when those monsters are human beings. Usually, their justification is "Well, we're the good guys and they're the bad guys", or some variation thereof. That's a shitty excuse, and that being a shitty excuse is the whole point of the game.

Games are fun. And what could be more fun than a guilt trip? Yay!

This kind of thinking is what has been holding our medium back since its inception.

I'll just put this in terms of writing for the moment. If you described the gore and screams of your victims in every scene the sensitive folk who are talked into participating will be revolted and reset the game. It wouldn't take long before no one but the strangest players keep on going. So if you really plan on tricking people, I wouldn't give them the blow by blow, and they'll supply their own "it's just a movie" mantra to see what's next.

Does that make more sense?

I'm not sure this fits. The game is a shooter, not a text-based game. Every fight they start, they're seeing first-hand rather than having it described to them. Either I'm misreading this, or this isn't really applicable to the game in question.

Well, to be totally honest, I'm probably just going to incorporate this theme into other games in a much more subtle manner and drop the idea of making an entire game about it. I have other, more subtle means that don't rely on turning the player act like a psychopath for the purpose of shaming them and only make them feel guilty if they were already.

You might be interested in how other games approached a similar problem. I cannot find it now, but there was a little 2D pixellated flash game called something like A Stranger or The Strangers.

If I remember correctly, you played as a kid in a space suit, with a little space dog in a suit, and you land your ship on a "little prince" sized moon and get out. As you moon jump right, these little green octopus-like aliens game start bouncing towards you from the side of the screen. You can shoot them with your blaster, but it turns out that these aliens are actually harmless. After not too long, you come across an enormous alien. She talks to you, welcoming you to the planet and explaining the little aliens are her babies. She wonders where some of her babies are gone, but she isn't too worried about it, she assumes they'll turn up later. She then escorts you back to your ship and waves you off.

This game avoided tricking the player, the established tropes are so strong that when a wave of aliens comes at you, blasting them is quite a natural response. Even for such a simple game, the experience of being confronted with the consequences of your decision was significant, or for me how much it felt like not having made an important decision. The description above cannot capture this feeling.