(The third secret poem appears to be another journal entry, again following the previous two. However, this also appears to be a letter as well.)
Dan,
I hope that I'm not too late, and I hope that you're able to see this.
Listen-things are a lot worse and way more messed up than either of us could have imagined.
I was right about the book, dude. It's connected to something way more evil and fucked up than any of us could have thought, and has a lot more influence over this world than it should.. Everything that happened in the book was a clue. I can't explain it here, but I'm urging you: BE CAREFUL!
It's already affected [XXXXXX] and I think it's been using her to slowly get to the rest of them. It might have already affected you, too. That's why it messed with your memories, that's why you've been seeing all these weird things.
I know that part of you still remembers. Part of you wants to remember. That's why you're still you.
You have to fight this.
You have to wake up and remember.
I can't lose you!
We have to end this nightmare!