spoilers for Tj's route
so, not only did Chase kill Sydney, but suppressed the memory of his death? I'm still not completely sure why the hysteria was focused on Chase alone, but maybe it had something to do with the fact that, he was embracing the events of that day, if that makes sense? also I'm 100% sold on the fact that after what happened to Flynn on his route, that he became a time-jumping ghost lizard, which is probably why Cameron saw him at the lake. oh, and then the towns hysteria happens two years later? maybe it was on Chase's return trip that he talked about with Leo. still no idea who "Sam" is and why he's a ghost voice in Chase's head. this definitely answered my question about Chase's relation to Sydney's death so maybe Carl's will answer who Sam is.
side note: maybe I'm fucked in the brain, and while these are horrifying, I can't help myself but feel so intrigued and fascinated by the horror shit.
Well, potential spoilers, but Carl's route actually has nothing to do with the "main" storyline. It's mostly just an info dump on the past, what's already happened. That said, it's still a great route.
Also, the backstory of the "voice" is explained in Jenna's route, not Carl. I recommend doing Jenna's route last because her good/happy ending is the best note to end the game on, and wraps up Echo nicely.