Alright, here it is, Lion786.
I have confused even myself (it's a big game that I've worked on for years, excuse me for that, I did not connect the dots), but it IS, in fact, the box puzzle.
After you opet the correct box, you will find the word "passage" inside, so putting the letters of that word in the alphabetical order will create the password...
SPOILER WARNING:
"aaegpss"
Hope that helped and that you can find your way further. Feel free to reply or e-mail us for further assistance! Best of luck!