Here is my 100% Achievement guide and full walkthrough for Tell Me Why (Chapter 2).
This is story related and believe cannot be missed.
While you are in the archives, you need to find boxes which hold relevant information regarding Mary Ann.
To do this, go on the computer, click on two tags (mainly Mary Ann) and it will either say nothing found, or there is something.
Once you go off, Tyler will utter another code but pay attention to the first 2 and last 3 numbers and letters. (That is what they are labelled as).
I believe this is timed and have about 5 - 7 minutes to get whatever you need before the Eddie cut scene begins.
Don't worry though, thats plenty of time to get whatever info you need on Mary Ann..
Go to 1:13:45 to see this
Hope this helps!