The SC will inform you that Sector 3 may melt down soon due to a malfunction in the Main Boiler's cooling unit. This ain't good news, as if the boiler blows it'll take the entire station with it. You'll now have 6 minutes to get moving over to Sector 3 to reactivate the cooling unit. Time to put on your running shoes. Once you regain control a timer appears on the screen and the music changes to a truly tense theme. The female computer voice will also continue to read out timer warnings, so the atmosphere couldn't be more tense. Leave Sector 5 without delay and burn over to Sector 3.
The target room we need to get to here is down below at the very bottom of this sector, first we'll need to get over to the huge shaft where all the dragon heads are lined up on the walls. Quickly descend the first red room and head through the opening down on the right wall. You can save plenty of time descending the large red chamber by running in from the Recharge Room with enough distance to fire up the Speed Booster - just run directly ahead and watch as Samus cleanly reaches the bottom-right corner.
Waste the dragon head up on the wall above in the next room and drop down beyond the shutter. Open it up, then walk over to the door you entered via and dash over through the opening on the right. Keep going to Speed Boost through the floor in the next room, then drop down and go right to finally reach the tall red shaft.
From here drop down to the very bottom and go left. In the following super-heated corridor use the ladders in the ceiling to make it over all the lava pits, but watch out for the fire bursts that appear often. Climb up the next shaft while freezing any dragon heads you find, they always come in handy as stepping stones. Go through the next room above to find a shaft leading up. Walk over to the dragon head and wait for it to come out of the wall before freezing it, do the same for the second head above to reach the next door. Make your way through the next large room while watching out for dragon heads and the small firebug creatures.
Cross the next small room to reach the Main Boiler, you should still have more than four minutes to go so we're on time. This place is a heated wreck, everything here looks like it's about to melt any second. Blast all the Sidehoppers you come across in here and jump up to the door up on the left wall. Fry the Eyeball Door quickly and go inside to reach the Main Boiler Control Room. Drop down to the control station down in the left corner of the room, but standing on the pad you'll find a human man wearing a lab coat! Yet how can he survive the intense heat of this area without any protection?
Shoot the man and he'll turn to look at Samus before turning into a large spiky-shelled Core X! This one is the Beam Weapon type, so fire missiles into the creature when it opens up and jump quickly to avoid its projectiles. Fry the beast and absorb the X to recover the Wide Beam ability! Quickly dash over to the pad to reactivate the cooling unit, you'll now have saved the station from instant destruction. Phew.
We now need to return to the Navigation Room, follow the path back up to the main areas of this sector. There's a few items to find along the way but they all involve diverting from the path, for speed purposes we'll pick them up later. You'll find on the way back that the Wide Beam really helps out a lot, so get used to it. Upon returning to the Navigation Room, the SC will give you more info on the X, apparently they can absorb the intelligence and memory of their prey, as the Core X you just defeated did with one of the crew members of the station.
The SC will then detect life-form readings on the Habitation Deck, which the SC shows you is up in the Main Deck. It will then restore power to the Main Elevator so we can go back up and investigate, there could be survivors up there. Leave this sector and ride back up the Main Elevator. Inside the wrecked wall up on the left where the SA-X first appeared you'll find Missile MD.04, but we'll get it on the way back down for convenience. Head over to the nearest Navigation Room. From here go right and ascend the shaft to the very top.
Ignore the giant creature blocking the green door on the right (only Power Bombs destroy these) and go through the left door to find an elevator. Ride it up to reach the Habitation Deck area. Save your game in the room on the right before heading left. In this next tall shaft, wait for the dragon heads to appear on the walls before freezing them. Climb up the shaft and go through the topmost door on the left.
You'll now be in the main Habitation Deck room, and a truly unusual sight awaits in the background of this room. You'll be able to see through a giant glass window into a lush vegetative area, where several creatures area wondering around inside. Look closely and you'll recognize these creatures as the Etecoons and Dachoras from Super Metroid that helped Samus out on Zebes by showing her how to perform Shinesparking and the Wall Jump trick.
Dunno how they managed to get here, but it's our job to rescue them from the X. Walk over to the shutter on the right and shoot out the large block in the floor to the right of it. Drop through to fall down to the next floor, then open the shutter there and use bombs to break through the solid wall on the left. Walk over to the green door on the right, then dash back to the left to break through Speed Booster blocks over in the corner of the room. Drop through to reach the bottom of the room, then go right and shoot open the shutter there to reach Missile MD.05 beyond.
With the missile tucked away run over to the left wall here and jump through to find a hidden shaft leading up. Ascend the shaft and go right to find yourself at the control station for the door lock. Step on the pad to unlock the door so the creatures inside can escape. As the monkey-like creatures jump out, the bird will follow closely followed by its little baby, thinking back you'll remember seeing the bird back on Zebes in Super Metroid with its baby as just an egg. They'll all run off to the right after you free them, we'll now head back to the Navigation Room (Samus has a short reflection on the creatures while riding down the elevator to the Main Deck).