Betrayal is a common plot event in the kind of stories that most RPGs lend themselves to. Whether your campaign is based around plucky adventurers going off to save the world against a dark god, about super spies during World War Two trying to stop the Nazi forces from opening a dimensional portal, or set in the far future where humanity is in the midst of its First Contact war, there is a good chance that a key part of the story will hinge on a betrayal happening. Unfortunately, between comics, books, movies, and other campaigns..well, Players are pretty wary of the betrayal aspect coming up, and in man cases will see it coming from a mile off. Not what you're looking for in your big dramatic reveal, right? So, let's take a look at betrayals and how we can make them memorable.
Core Aspects of Betrayal
Before we can look at anything else, we need to look at the core aspects of betrayal and how they work. First off, and most importantly, for someone to betray you, you have to trust them. This means that if you want your Betrayer to directly harm the PCs, that you need to put the time and effort in for the betrayer to gain the PC's trust. Only after the NPC has the PC's trust can he/she betray them, so that is going to be your first goal here every time.
Of course, you don't have to betray the PCs, which can make things a lot easier on you and really shake things up for the PCs. We'll talk more about that later.
The Fourth Wall Problem
One of the biggest problems you have in RPGs with this sort of story arc is the fourth wall. How many times while reading a book, or watching a movie, have you been talking to a friend and said "I'm just waiting for this person to betray everyone," or something like it? I'd be willing to bet fairly often, if only because humans are generally good at picking up on patterns and we'll see the signs for it. Now, in a book or movie, where the audience is non-participant in the story, this can add tension as we wait for the inevitable. In a RPG though, well, the audience is participant and will likely take steps to prevent the bad thing from happening.
What this ultimately means, is that the PCs will have an edge up on spotting betrayers because of the player's eye view they have. Any NPC that gets more than its fair share of story time, is important to the story. If that NPC is not someone high up above the PC - i.e., the person giving missions out - then it means that the NPC has some other role. Which generally means something horrible is going to happen to them, or that the PCs will end up being betrayed by them. What follows is a sense of wariness that most people can't help. It's not even really metagaming, because the player likely can't control it. They know something bad is going to happen involving that NPC (why else is it getting so much development time?), and so they brace themselves against that loss and look for reasons to not trust as much.
To fight this, the only thing you can really do is make a lot of NPCs important and balance the time accordingly. Have some NPCs important just because they are the PCs friend, or want to help out. Have an NPC love interest stick around and be a piece of the story that is important, but doesn't involve having to be saved, or betraying the group. Basically, you need to fill your game with false positives, so that the player's eye view doesn't have as easy a time spotting the coming betrayer.
Chance To Notice
The other big problem with betrayals, is that you need to give some lead in to it, or it just feels forced. Now, some games have ways around this, but in general you need to give some signs that someone may be a weak point or a betrayer in the future. This is another place where your PCs are likely to catch on quickly, especially when aided with what we discussed above. The answer here as well is to set down false positives. Give yourself options to use for when the time comes. Different ways it can play out. After all, if the PCs take time to stop Brenda from betraying them, that doesn't mean the enemies won't approach Gavin. This lets the PCs take action without necessarily derailing things, because you've already got other developed cases ready to go.
Of course, if the PCs hunt down and find every possible betrayal, then you have problems. At the same time, finding all those people took time. Time that the PCs weren't doing other things. So, take a breather, and figure out what ways that can make the PCs' lives interesting, without a betrayal.
Reason For Betrayal
Perhaps the most important story aspect of betrayal, you need to have a reason for the betrayal to happen. Desperation, a bribe, extortion, anger, revenge, something. Whatever it is, you need to have it, and you need to make sure the PCs know what it is. you also need to have seeded its beginning earlier in the story.
For example, in a sci-fi game, you could play up one NPC pilot constantly being jealous of the performance of the PC pilot. This then comes to a head in a "I'll show you" act of minor sabotage. Which, of course, comes into play on the worst time ever. Sure, it was supposed to just be a routine patrol, but it ended up being combat and the person's ship is now acting funny. However, when the PCs find out who did it and what happened, well, you have your pre-seeded reason for it, and it will come off a lot better.
Shaking Things Up
Like I said above, PCs are smart, and Players will often see betrayal coming. So, why not shake things up? Don't have the betrayal affect the PCs directly. Sabotage a friendly ship with betrayal, or the enemy forces. Use betrayal int he story, but not directly at the PCs. This way they have to deal with the fall out, but not the drama of "omg, someone betrayed us?!" Give it a shot, it can be a nice way to spruce things up.
Betrayal is a common plot element, but it isn't often occurring in the stories it shows up in. Why? Because it can get old fast, unless it is a key part of the story (first couple seasons of Battlestar galactica anyone?). You also want to becareful, because Betrayal is viscious for a good reason. It involves someone you trust knifing you in the back. A well executed Betrayal will make a fight harder than ever, and can even make a TPK happen if the players don't react well. So, be careful when you execute these things, and make sure you've planned for how it should go down. If it goes down otherwise, that's cool. Just give the PCs a way out to at least try for.
Did I miss anything? other thoughts, comments, or whatevers? Please sound off in the comments below.