I've been thinking a lot about the Star Wars: Edge of the Empire game my friends and I played a few years ago. Specifically, I'm thinking about the end of our first story arc, where we were trying to stop some villains from going to war over a planet. Partway through the session, two of our party got knocked unconscious - our pilot droid, and our lead talker/negotiator. During the story, one of our characters had obtained a few radioactive isotopes, so when patching up the droid, he decided to put the radioactive isotope inside the droid’s power pack.
Our GM, somewhat baffled, asked the droid to roll a Force Dice (one of the custom dice in Edge of the Empire). The droid rolled a dark side point, which meant the result would be bad… but the GM just said, “Okay, your droid stands up… he’s apparently been repaired…”
Now, as a GM myself, I realized the hidden meaning. Your droid is a dead man walking. At a moment that is dramatically appropriate, your droid will either die or explode. However, apparently everyone else at the table had a different notion… See, we still had one party member bleeding out, and this character who had (apparently) repaired the droid… well, he wanted to see what happened if we injected the radiation into our mortal friend.
I was baffled. Our GM was clearly baffled. And no one else at the table decided to object. Everyone agreed, “You know, I kind of want to see what would happen…” So he injected this radioactive isotope into a bleeding hero, and the GM said, “Okay, his eyes melt out of his skull and his flesh dissolves and he dies.” Because of course he does, because it’s freaking radiation.
In the aftermath, as our party realized that they had collaboratively killed one of their own, the objections began. And the defense of the player who had murdered two others? “I thought it would give him superpowers. I thought it would turn him into She-Hulk.”
When players get an idea in their heads, it becomes very difficult to dissuade them from that idea. Case in point, our now-murderer PC had come to the ridiculous conclusion that injecting someone with radiation would somehow be beneficial. Had we been playing a superhero game, an argument could be made in his favor. However, there had been nothing to suggest that the radiation was anything but ordinary, very dangerous radiation, and nothing in Star Wars has ever indicated that radiation gives you superpowers (unless that’s where midi-chlorians come from or something). The idea that (A) our player somehow thought this was how radiation worked, and (B) everyone else was curious to see if he was right, is laughably absurd.
But that’s how ideas work. When a player gets an idea in their heads, it becomes very difficult to dissuade them of it. If you introduce a character that the players dislike, then every encounter with them is in the context of, “Yeah, this guy is an ass.” Even if that character is doing good things, your players will still somehow frame it through the negative bias they have towards them.
This is a general rule in fiction overall - you have to be very conscious of how characters and concepts are introduced in a story, in order to ensure no one comes away with the wrong meaning. Once your audience has the wrong idea about the story, it is nearly impossible to convince them to change it.
But how do you solve the problem? Well, let’s carry this example further… If you introduce a character your players are supposed to trust, and the players somehow think this person is evil, it doesn’t matter what your intention was; you have introduced a character the players distrust. Given that, how do you move forward? This person can’t fill the role you intended for them, because the party likely won’t work with them, or will keep them at a distance at the very least.
But with a bit of trickery, you can use this to your advantage. Your players are already waiting for the other shoe to drop - you can turn their expectations on their head by having this character come through for them in a time where he/she did not have to. Maybe the party gets in trouble, and this character bails them out? Well, that might work… or it might just further prove to the party that this character has an ulterior motive. The other option is to embrace the fact that your party doesn’t trust this person… because you’ve been given the opportunity for a red herring reveal.
For those unfamiliar, “red herring” is a literary term for a misdirect - the audience seems certain that they know who the villain is, but then the story reveals that this person is totally innocent (at least of being the main villain, though they might be guilty of other offenses). Red herrings are very difficult to plan in role-playing games, because they rely on predictable interactions with your NPCs. However, if you know your group mistrusts someone who you know is not actually evil, then you can set your players up for a fall.
Ideas are stubborn creatures; once your players have made a judgment about something, it is almost impossible to correct it. Usually, this issue arises from something the GM has failed to make clear (though there are rare cases where it stems from the facile notion that radiation is not intensely lethal). If your players believe something you know to not be true, you have to either catch it early, or weave their expectations into the story. If they say, “Oh so, this guy is coming to town because he’s trying to buy up a whole bunch of land!”, then it may be worth breaking the fourth wall and just clarifying, “No, they said he’s coming here because he’s already inherited the land; he’s just coming to appraise what he already owns.” Breaking the fourth wall to offer a bit of clarity, otherwise you’ll find your players think they know what’s going on, but are entirely mistaken.
If, however, you weave their expectations into your story, you can come across as a lot smarter than you actually are. If executed correctly, your players will think you’ve had a twist planned the entire time.
As for what happens when your players inject themselves with radiation… well, players are the biggest variable in gaming. More than dice or luck, your players and their unexpected actions are what can really keep you guessing.