After getting the digital camera, go back to where the DARPA chief (Decoy Octopus) died. If his body is still there, take a picture of it then save the game. Restart the PlayStation and select "Special" at the main menu. Select "Photos" and play around with the red, green, and blue. Eventually, you will reveal Decoy Octopus. This also works with Meryl. Take a picture of her just before you enter the room to fight Psycho Mantis, and immediately after she starts to act strange. Then use the same steps done to reveal Decoy Octopus and you will reveal Psycho Mantis, Meryl's possessor. Note: If the DARPA chief's (Decoy Octopus') body is not in the cell when you return with the camera, do not worry. Play through the game then begin a new game from the same save file. The camera will now already be in your inventory.