So I missed the first two, the prologue and chapter 1. I found the one in chapter 2. And it wont let me exit the nightmare level. The exit is locked. It has a little lock icon on it. Not sure what the deal is. Do you have to find them and complete them in order? Or is there new special things they added to the old 3D levels that you have to find to unlock the exits?

I've been all over the level twice and I don't think I missed anything, so I am thinking they have to be played in order. Which is stupid if that is the case. Because not everyone is going to find them all on their first playthrough.

I'm guessing this is a General Discussion bug again.

Which game???

Guess you got hit with the General Discussions game bug...

Now its in the correct place. Stupid bug.

And I found my answer. I didn't pick up the stupid key. I swear I did.

Did you find the secret rooms in the Nightmare levels? They may not be obvious if you have never played Wolfenstein 3D.

you need to find the big key.