Briefcase # 13
You begin the level by climbing through the basement and walking out the front door of a small house. Before running off to splatter pod-people aliens, make sure you check behind the car to the left. One of the elusive brown briefcases will be there (the color of the case has no effect on anything).
Briefcase # 12
For some reason, the game decides it’s a better idea to crawl through a flooded basement than bust open a door on the first floor or climb over a small fence. After you find the flooded basement’s stairs, climb out and look in the room to your left. We’re still not sure exactly where this case is, but walk around enough and you’ll bump into the stupid thing.
Briefcase # 11
Towards the end of the level you have to fight your way through a gas station and then you’re shot at by aliens in a diner. Don’t run straight up to the diner. First, look to the right of the area between the gas pumps and the restaurant and find briefcase eleven behind some army vehicles.
Briefcase # 14
After two Ravagers blast through a wall early in the level, kill them and go through the hole they created. You’ll see a tent to the left. Briefcase fourteen is sitting on a table inside.
Briefcase # 16
After locating Doc Malakov, follow the tunnel to the left to find briefcase 16. Don’t worry, the Doc won’t mind waiting for you.
Briefcase # 15
The second time you’re chased by the swarm monster, look for a hallway on your left that contains the following: One dead soldier and one briefcase.