After you destroy the Nightmare, Adam tells you destroy the Rogue Security Robot, which is now in Sector 6.
Find the Robot
In the Sector 6 Navigation Room, Adam tells you to leave NOC as soon as you have destroyed the Security Robot, because the SA-X is tracking you.
After you go through the Save and Recharge Rooms, go to the right until you can go no farther right. Go downward until you can go through a door on the left. Go to the far left side of this room and use a Power Bomb, then go to the left and go through the door on the left. This room has little flying creatures, and some Puyos at the bottom. Go to the bottom of this room and go through the door on the right. Walk to the right to fall through some Pit Blocks, then drop a bomb against the ceiling if you can, or just drop a Power Bomb to reveal rungs in the ceiling. Then go through the door on the left.
Go to the left and go through the door on the left. There are Bulls floating around in this room. Go to the bottom of the room and go through the door on the left. There are more little flying creatures in this room. Go to the bottom of the room. You can go through the door here to find a Save Room. Outside of the Save Room, go to the left side of the room shoot the floor there. Go down through the hole, then go through the door on the left. Go to the far left of this room and the computer will warn you that you can't enter without authorization.
Go back the way you came, and eventually you will encounter the Security Robot.
If there aren't any rungs in the ceiling, drop a Power Bomb to reveal them.
The Security Robot has electrified the water, so avoid touching it. Hang from the far left side of the ceiling rungs. Shoot your beam to destroy the Missiles that the robot shoots at you. When the robot runs to the left side and bumps into the step, hold L and shoot as many Missiles as you can at the robot's back before it jumps out of the way.
After you have damaged the robot enough, it will turn into a Wave Core-X. It has an eye, so jump over the beams that it shoots. After you defeat it, take the Core-X to regain your Wave Beam ability. This beam can pass through walls and other obstacles.
Sector 6 (NOC)
Exit through the door to the right. Go to the far right, where there is a Missile Tank that looks inaccessible. Now that you have the Wave Beam, it will pass through the gate and hit the flashing light and open it. Shoot at the red light to open the gate and get the Missile Tank.
Go back to the room where you killed the Security Robot, then go back to the gate where the robot said that you could not go through. With the Wave Beam, your beam will go through the gate, so shoot the red light and go through. Roll through the tunnel, and you will find yourself in the Restricted Zone.
Roll to the left to fall through some Pit Blocks. Go through the door to reach a Save Room, then in the Save Room, go through the door on the left. Keep going to the left and you will find the Restricted Laboratory. There are some interesting specimens in the background. Keep going through the lab until you can go no farther. When the ground starts shaking, go back the way you came.
You will see a cutscene, and a one minute timer will begin. Space Jump upward while avoiding the Metroids. They will knock you downward and drain your energy if you touch them. When you reach the top of the room, go through the door to see a cutscene.
Go through the door on the right and use the Navigation Room. Adam orders you to return to your ship to escape from the station.
Go through the door on the right and go up the elevator. After a monologue, you will be in Sector 1 (SRX).