Part 1[edit]
Captured: After having been caught by the enemy, you will "wake up" inside a closed cell with no doors. Although all of your equipment and weapons have been taken, you still retain the ability to use the Transceiver. Big Boss will call you when you arrive. He will declare your infiltration mission a success, and order you to find Gray Fox. He says, "check the way," but this should say "check the wall". The way you do this is by punching the walls. Most of the time, your punches will have no effect, but one portion of the wall will collapse when you punch it, creating a doorway. When you find the right place, pass through the hole you created. In the next cell, you will find Gray Fox. Rescue him and he will tell you more about Metal Gear. He will inform you that there is only one way to destroy it, and the only person who knows the method is the creator, Dr. Pettrovich, who is being held captive somewhere in the building. With Gray Fox rescued, your next concern is escaping. Once again, you need to check the walls. After a thorough search, you will find that the south wall will collapse slightly to the left of Gray Fox. Punch it and step outside into room A1.
A1: Your only two choices are a locked door to the north for which you don't have the correct access card, and a passage to the east. Head east to room A2.
A2: As soon as you arrive, a mini-boss will announce his name, Shotgunner, and inform you that no one has ever escaped before. You're about to be the first, but you'll need to find some way to even the fight out. Stay on the bottom of the room and walk through the right door. Inside, you'll find a sack containing all of the items you had in your possession when you were captured, including all of your weapons. You should have at least four remote controlled missiles at your disposal, so activate them and leave the room.
Once Shotgunner is taken down, prepared card 2 and approach the left door. Inside, you will find access card 3. Unfortunately, the north door of A1 is not locked with card 3, so you still can not examine it yet. However, the east door of A2 is accessible with card 3, so open it and head to A3.
You should examine your inventory when you have completed the fight with Shotgunner and are safe. You may notice that you picked up an extra item since you found your equipment. A radio device labeled transmitter will be in there. It's a tracking device, and it will alert all of the guards to your presence every time you enter a room, no matter how stealthy you are. If you see it in there, use it like you would a ration, and it will disappear, restoring your element of surprise.
A3: Once you enter this room, you will notice a dog sleeping by the entrance. Punch or shoot the dog. If you do nothing and ignore the dog, the dog will wake up and attack you, so you are better off removing it. Open the bottom left door with card 2. Inside, you will find the body armor. Wearing this armor will reduce the amount of damage you take from bullets in half. You must have this item activated for it to be effective. Exit the room, deal with the dog, and follow the upper path east to A4.
A4: Follow the path as it leads you to the door in the upper right. Open it with card 2, and inside you will find the bomb blast suit. This item is absolutely essential in order to pass through the wind barrier on the roof of building 1 and make further progress. Then exit the room, and enter the lower portion of the room. Before you examine the southern door, which is actually the exit from the building, return west once more to A3.
A3: Back on the right side of the room, approach the lower right door, and open it with card 3. Inside, you will find the enemy uniform. It won't come in handy for some time, but you will be glad you don't have to backtrack to collect it when the time comes to use it.
Return west to A4, and exit through the southern door with card 3. You will appear outside of building 4. Refer to this page to learn how to make your way back to building 1 so you can continue your investigation.
Part 2[edit]
Note that this walkthrough assumes you returned to the building 4 via the secret tunnel that connects this building to building 5. If you returned through the entrance, you will walk back to the room where you rescued Gray Fox and open the top door with card 6. Please note that this is an expanded view of the same map presented up above.
You will arrive through the door at the top of A1.
A1: When you enter this room, it will be pitch black. You will absolutely need the flashlight to make it through this section. If you did not find it, you will have to exit back through building 5 and approach building 4 from the front. Activate the flashlight so that you can see the room around you. Diane will give you a call in this room and advise you to watch out for pitfalls. There happen not be any in this room, but there are plenty to come. Take the far left path south to B1.
B1: Diane will continue to call you to warn you about pitfalls. Hug the bottom of the top row of crates as you make your way to the right. Before you step out to the open space on the far right, come down to the bottom row of crates. Your goal will be to slip around the right edge of those crates before the pitfall on the right opens all the way up and swallows you. This can be difficult, and must be executed perfectly, or you will fall in. Once you're past the pitfall, continue south to C1.
C1: To make it safely through this room, come down to the top of the crates on the right. Walk down until you're along side of them, then start walking left. You should start to see a pitfall open to the left. As it does, start moving south to get away from it, but watch out for the pitfall which will open below you. Get as close to the center crates as you can before moving all the way down to D1.
D1: This is another extremely challenging room. To clear it, you must walk up to the left edge of the top crates and quickly walk down and around the corner before the pitfall to your left fully opens. Then cross right until you are even with the left edge of the right crates, and walk straight down to E1.
E1: There are three pitfalls along the bottom of this room. Your goal is the door in the middle. Come down between the pair of crates, hugging the right side. Very quickly duck around the corner to the bottom. A pitfall will appear below you, while another one starts opening to your left. You must be standing squarely on the small two-tile platform between them which leads to the door, or you will fall down one pitfall or the other. If you survive, run down and open the door with card 1.
F1: Four more dogs guard this room. Deal with them if you have to, and run down to room G1 below.
G1: A pair of soldiers will be standing guard here. Take out the right one, then activate card 6 and approach the door on the right. Once inside, you won't see anything. While your first instinct may be to punch the walls in search of a weak point, be very careful in this room. As you approach the right wall, you are likely to trigger a pitfall. If you do, run away and let it expand. Then return to the wall, and carefully punch various sections of it until you find the weak point. Pass through the hole you created and on the other side, you'll find Ellen. Rescue her and she will thank you for saving her.
At this point, you must return to Dr. Pettrovich to learn the secrets he has to share with you about the Metal Gear project. You can do this by returning through the dark pitfall tunnel, or by exiting the building and approaching the entrance to building 5. Either way, you cannot complete the game without speaking with the doctor again.