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You have to make the character into a real person who the audience believe certain things about. In particular that the sidekick is loyal to the protagonist not the or some set of ideals but the pe...
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Source: https://writers.stackexchange.com/a/46707 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
You have to make the character into a real person who the audience believe certain things about. In particular that the sidekick is loyal _to the protagonist_ not the or some set of ideals but the person they're fighting alongside and yet determine to eventually betray, creating a strong bond between those characters will give the audience pause if/when they suspect the outcome of the situation. They won't/won't want to believe that "Sid the psychic sidekick" is going to betray his friend and fearless leader this lets you hide their intentions as long as possible, the less your audience suspects the better the reveal becomes. The trick is that in order to avoid whiplashing your audience you need to point out what your villain is without the audience realising that's what you've done. One of the better ways of doing this is an apparent redemption narrative wherein your villain starts out disagreeable and seems to "turns their life around" while with the protagonist they still have shadey dealings with people from their "previous life" as they "wrap up loose ends" and "pay off understanding obligations" etc... All the time they're actually setting up the big fall of the protagonist. One thing to note is that no matter how you dress it or hide it there are always going to be readers who make an early intuitive jump, like my father watching _[The Village](https://en.wikipedia.org/wiki/The_Village_(2004_film))_ for the first time and realising what was going on during the first town council meeting and spending the rest of the film being disappointed. Sometimes the ones who make that jump are your beta-readers so it pays to get several opinions on these kinds of stories to see if you're actually to transparent or just have a savvy first reader on your hands.