After discovering a specimen infected with the X parasite, Samus regains her missile ability. Electrical interference shuts down the power and Samus must find an alternate route to investigate the bio-signs.
Find an Alternate Route
Go right to exit the Navigation Room, then jump onto the platform to the right. Jump to the next platform and you will see a glowing panel in the wall. Shoot it with a missile (hold R while shooting to shoot missiles). Jump through the opening that you created, and go to the right.
There is a living barrier (Gelon) to the right. Shoot it with three Missiles to destroy it. Walk to the right wall and you will fall through some Pit Blocks. Jump up over to the other side of the wall to the left, then shoot the wall to the left to break it open. Go through.
There is a purple blob down below that will turn into a Zombie when an X enters it. If you get too close to the Zombie, it will crouch and attack. If it crouches, it will be lower than your beam can shoot, but you can press down to crouch, or you can hold the L button to shoot diagonally. If you hold L and press down, you will shoot diagonally downward.
Stand on the floor to the right, which is made of Pit Blocks. Continue to the left where there are more Pit Blocks in the floor.
Jump onto the ladder to the right and climb up to get over the wall. Drop down to the right, then drop down to the left. To your right is a Missile Tank upgrade. Collect it to increase your missile capacity by 5.
Go down below. First, go to the left. If you look at the map in the top right corner you see a circle in this room. This means that there is a hidden upgrade in this room. The upgrade in this particular room is hidden in one of the "steps" on the left wall. Shoot the top step to find a Missile Tank. Exit right.
Kill the Zombie and exit right to reach the Main Deck.
Kill the Zombie here. You will soon fight a boss, so if you want to save, don't go to the right. Instead, jump up to the stairs and exit right to reach a Save Room.
Return to the Main Deck and go down and right to reach a Living Door (Gadora) blocking the way. You have to shoot the eye when it opens, but sometimes the eye will be covered with a yellow membrane. If there is a membrane, the eye will shoot the membrane at you, so be sure to jump over it. The membrane can't be hurt with weapons, so you have to wait until the eye opens again. If you can see the pupil of the eye, shoot it with a Missile.
While you attack the Gadora, be careful of the Zombie behind you. It will keep coming back to life as X parasites keep floating into it.
Once you hit the eye of the Gadora three times, it dies and leaves behind a red X, which refills 500 units of energy and 50 missiles. Go through the door that the Gadora was blocking.
Jump up against the metal railings to hold onto them. Then press the button in the opposite direction of the wall, then jump to go to the next railing. When you reach the top of the wall, go to the right to fall to the lower area. Go to the right to find an Energy Tank.
There is another upgrade that you can obtain before you battle the next boss. Go to the far right edge of the platform where you got the Energy Tank. Stand on the metal railing and shoot a missile at the ceiling. If you didn't hit the missile block, try shooting different parts of this ceiling until you find the missile block. After you destroy the missile block, shoot your regular beam (not a missile) upward through that hole, then jump up through the hole and go to the right. You will find another Energy Tank in the next room.
Go back the way you came, and in the room with the metal railings, drop down the tall room to the right. Down below you'll fall through some Pit Blocks and you end up in a room with a Core-X. It becomes your first boss, Arachnus, which was first seen in Super Metroid.
The front of Arachnus is vulnerable, but its back will deflect Missiles and your beam, so don't shoot its back. Rapidly shoot Missiles at the front of Arachnus. If you run out of missiles, just shoot your beam at it. If Arachnus spits fire, jump up onto the railing above you and hang from it to get out of the way. If Arachnus scratches at the air with its claws, it is going to shoot a blue energy wave at you, so be prepared to jump over it. If Arachnus curls into a ball, hang from the railing and jump over Arachnus before it rolls into the wall.
After you kill it, it will turn back into a Core-X, surrounded by free-floating X that you can collect to replenish missiles and energy. If you need more X, shoot the Core-X with your beam to make it release more.
The Core-X will float around trying to hit you, so you have to keep jumping over it or running under it. Hit the Core-X with a Missile, then wait for it to stop flashing before hitting it with another Missile. After three Missiles, the outer shell will be destroyed, allowing you to collect the inner Core-X. When you collect this Core-X, you regain your Morph Ball ability.
Press down twice to curl into a small ball. You can roll around small spaces with this ability. Also, if you hold a ledge that leads into a narrow tunnel, you can press up to automatically enter the tunnel as a ball.
Find a Navigation Room
Morph into a ball (press down twice) and roll left through the tunnel. On the other side, press up to stand up. Jump over the blocks, then jump up to hold onto the ledge. Press up to morph into a ball, then go to the left.
Climb up the ladder, morphing into a ball at the top to roll through the narrow tunnel on the other side. Go to the top of this ladder, then press left and shoot into the narrow gap to destroy two blocks in your way. Hold onto the ledge and press up to roll through. Kill the Zombies and roll through the passage to exit to the left.
Continue going to the left. Up above, you can shoot the Gelon and go into the door beyond it to find a Recharge Room. Afterward, leave the room and go back down and go through the door to the left. You will go through a Save Room. Go to the left until you reach a tall room. Go to the bottom, then use the bottom-left exit to reach the Navigation Room.
Adam tells you to investigate the SRX sector, where X parasites are disrupting the breeding environment.