This secret can be obtained without even starting the game. You must have also bought an official copy of the game. You cannot see this secret if you have rented the game or burned a copy. On the game case cover, you can see the title and the game summary. If you turn the game case cover inside-out, you can see a completely different cover. There will be text at the bottom of the cover. If you read the text, you can see a prompt sent by Gabe Logan. The text shows different kinds of weapons that can be found in the Carthage Mission. (first level).