Surprising the player through a twist in the game's story is either a hit or a miss. It's very important that you hit, and it's important that you hit hard.
Here is a very simple tool that will allow you to better surprise the player with whatever twist you have planned. Not only will it improve the element of surprise, it will also decrease to a large extent the players' ability to outguess you, the story designer.
We all know the key to a creating a good surprise is to convince the players that the opposite is true. The problem is that denying something or insisting on a truth is the best way to get skeptics to believe in the opposite, thus spoiling your surprise.
The real key, then, is to establish your premise without ever being noticed.
Here is the method, in four steps.
Step #1: Decide on your surprise.
This is the easy part. Write down whatever you want the surprise to be. Don't worry for now about making it believable or surprising.
For our example I'll choose a cliché, something we expect our savvy players to actually suspect. In this case: A character that has been there from the start and is very close to the player is actually a robot.
Step #2: Find the opposite of your surprise.
For your surprise to be truly surprising, you need to convince your player that the opposite of the surprise is true. You need to be sure what that is.
In our example: We need to establish that the character is human. We must convince the players of this premise for the surprise to be big.
Now let's find a way to establish the premise.
Step #3: Find the players' hidden assumptions about your false premise
Here's where it gets complicated.
You have your premise, chosen in Step #2. The last thing you want to do is to actually say it out loud in any way. Nor do you want point to it, even for a second: Remember, this is true! That will immediately get the skeptics who play the game (and you know most gamers are skeptics) to suspect that the opposite is true.
So we'll take a step back and look for something else.
Find the player's hidden assumptions about your premise. This means that you must find something, that if you show it to the player, he will immediately become subconsciously convinced that your premise is true, without ever thinking about it.
It sounds crazy, but the truth is that our mind is constantly bombarded with a whole lot of data, and decides on things on a subconscious level all the time. You need to train your mind to find your own hidden assumptions.
It's best to show with our example:
What subconsciously makes us think that someone is a human and not a robot? Here are a few options:
1. Humans enjoy food. If the player sees our human-like character enjoying pasta (or whatever), he will become subconsciously convinced the character is human.
2. Humans give birth. If the human-like character is the birth mother of the player's character (and if that is established without a doubt), the player will have no doubt that the mother is human.
3. Humans have nightmares. If our non-human character was female (which most people associate with being slightly more emotional and therefore less robotic) and was having terrible nightmares every night, to which she will react emotionally and seek solace at night in the arms of our male hero (played by the character). Not only that, but she will fail to calm down and not be able to fall asleep (that way it doesn't look like she's manipulating the hero). The player will subconsciously assume the character is human.
Step #4: Deflect attention by making another point while making your real point.
Step #3 is not enough to make a surprise surprising. For one thing, don't overdo it, don't make too big a point of anything established in step #3, and don't show the character's humanity (in this case) too many times. Establish your premise once, and that's enough.
However, there is one more step to make the cover-up complete.
When making your point (establishing the premise subconsciously) make sure that at the same, exact time you are making another important plot point. Players subconsciously assume that only one important thing is being told to them at one point in time, so make sure that your step #3 makes another point that is also important to the plot.
In step #3 we had three different options, from which we will actually need to choose only one for our game. But let's see how we would handle each of them when taking the next step:
1. The human-like character is eating and enjoying pasta.
We absolutely do not want to show the character eating pasta without anything else occurring, that would raise suspicion that we are trying to say something. So: There will be a scene (for example) in which there is a meal of friends (say all the characters are cops). They're eating pasta and enjoying it. But the pasta is poisoned! One character dies, the other are sick and rushed to the hospital, or their health goes down. The bad guys tried to get rid of all the good guys! We lost a few good men, now let's go get them! (See? Deflection.)
2. The non-human character is the player's mother.
First of all, the mother should look a lot like her son (who is human), and that point should never be mentioned aloud. We should let the players see it. Next, the deflection: There is a scene, in the beginning of the game, in which the mother and the father are shot at. This was an assassination attempt in order to convince the player's character not to pursue his line of investigation. The father dies. The mother survives (perhaps shot and bleeding, perhaps not). This sets our hero (the player) on a vendetta to get all those responsible. (See? Deflection. We've established she's the mother, and therefore human, while actually making a plot point about assassination.) The mother can then stay in the background from that point on, and never make a big point of her being there (unless she is necessary to the plot).
3. The non-human female character has dreams.
In this example, the dreams themselves can be a plot point. The female character dreams about a traumatic event that happened in the past and is being repressed by her mind. The dreams give us a window into those events, events which the player must uncover in order to find out the truth about the bad guys' plot. Again, in advancing the plot about the bad guys, we've subconsciously established the character is human. And the beauty of it is that we never had to even hint at the fact.
Surprises can be anything, and these rules apply to all surprises.
We need train our minds to find what it is that subconsciously convinces us of certain facts. Once we get used to these kinds of thoughts, manipulating the players' beliefs becomes very easy.