Yeah, the camera has likely been there for a while. Vinny might have very well installed it before he left, eliminating the need for a traitor for that.The camera has been there for a long time, so it was at the very least definitely not installed during the Halloween party. The photo of the threesome with Jacob, Arieth and Derek was clearly taken from an angle that makes it clear it came from a security camera. Before all of this, you could spot a ladder in the janitor's closet that was placed right around close to where the camera has been installed later on. Because of the threesome picture, it's evident that it couldn't have been installed during the mansion repairs either even though it is suggested by Derek that it could've been.
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Jamie is the one that's being set up to be the "traitor", even though there actually isn't one as far as active DIK members go. He lost his phone in EP3:
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Take a look at who he was dancing with right before he lost it:
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He's also the one who walked by past the library's window after MC's birthday party:
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During one of the free roam events, he tells the MC that he can't get any sleep lately which is why he went for a walk at night.
He's also the one that installed the lights when the mansion was being renovated by the DIKs:
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He's the first guy that the MC and Derek will suspect when they learn this after they actually ask Rusty or the others about who it was that installed the new lights back then. Other than that, Jacob has already confirmed that he's somewhat suspicious of the MC himself, given that he asked him whether he's a "100%" with the DIKs or not. It'll probably begin with them suspecting the new guy (MC) and after that it'll be Jamie before (and if) they realize that there is no traitor and they're being deceived on purpose.
Jamie might have been a "traitor" unknowingly, through the lost (or stolen?) phone, but that could also be a red herring.
Now, the picture with Sally is interesting and gives me an idea. We already know Sally is coming to MC's room in the coming episode, atleast on one path. So far most people seem to think it's for a sex scene. But what if she's involved? What if she does something in his room to make him look guilty? Now that would be a plot-thickening twist.