Doom 3 Walkthrough Alpha Labs Sector 4

September 12, 2016 (Last Updated: ) | Reading Time: 11 minutes

This Doom 3 walkthrough is divided into 27 total pages.

You can jump to nearby pages of the game using the links above.

Alpha Labs Sector 4

Doom 3 Walkthrough - Doom 3 337
Doom 3 Walkthrough - Doom 3 337

Sarge updates your objectives. Ammo is on the desk ahead, and armor is behind the crates to the left. Heal at the health station farther left then continue through the door. Head left and Kaczynski asks you to let him out of the chamber.

Doom 3 Walkthrough - Doom 3 338
Doom 3 Walkthrough - Doom 3 338

Note this panel to the right. It has two options, ACTIVATE and OPEN.

Doom 3 Walkthrough - Doom 3 339
Doom 3 Walkthrough - Doom 3 339

You want to choose OPEN CHAMBER to let the nice man out.

Doom 3 Walkthrough - Doom 3 340
Doom 3 Walkthrough - Doom 3 340

If you were to choose ACTIVATE CHAMBER, the poor man is...processed.

Doom 3 Walkthrough - Doom 3 341
Doom 3 Walkthrough - Doom 3 341

If you fail to free the him, these two Z-Sectors charge in through the door behind you.

Doom 3 Walkthrough - Doom 3 342
Doom 3 Walkthrough - Doom 3 342

Ride the nearby lift down and talk to Kaczynski - assuming you rescued him.

Doom 3 Walkthrough - Doom 3 343
Doom 3 Walkthrough - Doom 3 343

Grab the Chaingun briefing video and Michael Abrams' PDA on the counter to the right. Listen to the Abrams audio log and learn that the BFG is in his office. He's requested a door code of 901, but the "Invalid Number in Code" email reveals that the 0 has been replaced with a 3, making the code 931. Use the blue panel seen here on the left to disable the security lock on the cabinets along the right wall.

Doom 3 Walkthrough - Doom 3 344
Doom 3 Walkthrough - Doom 3 344

Grab the grenades, armor, and ammo seen here. This is a very handy room -- it would still be locked if you hadn't rescued Kaczynski.

Doom 3 Walkthrough - Doom 3 345
Doom 3 Walkthrough - Doom 3 345

Proceed through the now-unlocked chamber.

Doom 3 Walkthrough - Doom 3 346
Doom 3 Walkthrough - Doom 3 346

This Imp attacks, followed by a Z-Sector. An ammo belt is to your left.

Doom 3 Walkthrough - Doom 3 347
Doom 3 Walkthrough - Doom 3 347

More Z-Sectors attack from that overpass ahead, followed by a swarm of Trites. Grenades and a medkit are to the left.

Doom 3 Walkthrough - Doom 3 348
Doom 3 Walkthrough - Doom 3 348

Climb the stairs and battle these two Z-Sectors.

Doom 3 Walkthrough - Doom 3 349
Doom 3 Walkthrough - Doom 3 349

This secret room opens as you pass. Battle the Z-Sector inside and the series of Trites that ascend the stairs. Inside the room you'll find armor, a medkit, a clip and shells.

Doom 3 Walkthrough - Doom 3 350
Doom 3 Walkthrough - Doom 3 350

A voice near this door on the left says, "Come here."

Doom 3 Walkthrough - Doom 3 351
Doom 3 Walkthrough - Doom 3 351

The voice beckons, "Follow me." These bloody footsteps lead you to this door, where everything goes red and you hear a baby crying. Freaky.

Doom 3 Walkthrough - Doom 3 352
Doom 3 Walkthrough - Doom 3 352

Returning through the corridor, you'll find this supply cache, including armor, cells, and a medkit.

Doom 3 Walkthrough - Doom 3 353
Doom 3 Walkthrough - Doom 3 353

Head through the door on the left and Sarge tells you there are two ways to proceed, both listed on this display. You can activate the EFR system, good if you like jumping puzzles, or extend the service bridge, better if you prefer fighting. Henry Nelson's PDA on the right has the code 651 for storage cabinet 064 -- only accessible for those who extend the service bridge. On the other hand, you'll get the plasma gun in this level if you activate the EFR, plus access to another storage area.

Doom 3 Walkthrough - Doom 3 354
Doom 3 Walkthrough - Doom 3 354

Before we tackle the two paths, here is a diversion for those who really like a challenge. Descend the ladder to the right. You'll find a medkit and an armor belt.

Doom 3 Walkthrough - Doom 3 355
Doom 3 Walkthrough - Doom 3 355

Grab them and this Imp appears. Not too hard, huh?

Doom 3 Walkthrough - Doom 3 356
Doom 3 Walkthrough - Doom 3 356

Now for the tough part. You'll find armor next to this storage bin. Approach after reloading your shotgun and another Imp spawns...

Doom 3 Walkthrough - Doom 3 357
Doom 3 Walkthrough - Doom 3 357

And another, and another...

Doom 3 Walkthrough - Doom 3 358
Doom 3 Walkthrough - Doom 3 358

A total of six Imps in all! This is a tough challenge, but you will be rewarded.

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Doom 3 Walkthrough - Doom 3 359

The bin opens to reveal this cache of cells, grenades, a clip and an ammo belt.

Doom 3 Walkthrough - Doom 3 360
Doom 3 Walkthrough - Doom 3 360

Return up the ladder. If you choose to activate the EFR, this platform moves into place, allowing you to jump across to the other side of the room. If you prefer to extend the service bridge, you can skip ahead.

Doom 3 Walkthrough - Doom 3 361
Doom 3 Walkthrough - Doom 3 361

Leap onto this bridge as it rotates into place. The door ahead is locked, so jump off the bridge when it arrives at the unlocked door on the right.

Doom 3 Walkthrough - Doom 3 362
Doom 3 Walkthrough - Doom 3 362

Advance into the room and this maggot spawns, then another. Armor and ammo are in the right corner.

Doom 3 Walkthrough - Doom 3 363
Doom 3 Walkthrough - Doom 3 363

Defeat both maggots then use this panel to start the EFR processing.

Doom 3 Walkthrough - Doom 3 364
Doom 3 Walkthrough - Doom 3 364

A third maggot spawns as you exit. Defeat the maggot and leap back onto the rotating bridge. Leap across to the now-unlocked door on the right, guarded by a Z-Sector. A running jump is essential for success.

Doom 3 Walkthrough - Doom 3 365
Doom 3 Walkthrough - Doom 3 365

You now have a choice. Unlike those folks who chose to extend the service bridge, the door on the left is optional for you. If you prefer to avoid a difficult fight, jump onto the moving platforms on the right and skip ahead.

Doom 3 Walkthrough - Doom 3 366
Doom 3 Walkthrough - Doom 3 366

This is a tough room. Start with a grenade toss to this Z-Sector on the right. Retreat into the hallway immediately.

Doom 3 Walkthrough - Doom 3 367
Doom 3 Walkthrough - Doom 3 367

I found the chaingun to be the best bet on the remaining Z-Sectors, one to the left and one down the middle. Just remember to save some chaingun ammo -- you'll need it at the end of the level.

Doom 3 Walkthrough - Doom 3 368
Doom 3 Walkthrough - Doom 3 368

Enter and this maggot spawns behind you. Search the shelves for supplies, including the three medkits seen on the right.

Doom 3 Walkthrough - Doom 3 369
Doom 3 Walkthrough - Doom 3 369

A second maggot spawns once you walk behind these shelves. The door on the left is locked. Backtrack to the hallway.

Doom 3 Walkthrough - Doom 3 370
Doom 3 Walkthrough - Doom 3 370

Hop onto one of these moving platforms. Take a second hop onto that red pipe to the right.

Doom 3 Walkthrough - Doom 3 371
Doom 3 Walkthrough - Doom 3 371

Stashed away in the corner you'll find armor, cells - and the plasma gun! Tuck the plasma gun away for now -- you'll need it at the end of the level.

Doom 3 Walkthrough - Doom 3 372
Doom 3 Walkthrough - Doom 3 372

Drop back onto a moving platform, dodging obstacles along the way. On the left is an alcove where you'll find armor. This room on the right is only accessible to those who've extended the service bridge.

Doom 3 Walkthrough - Doom 3 373
Doom 3 Walkthrough - Doom 3 373

Jump and duck to avoid these spinning blades.

Doom 3 Walkthrough - Doom 3 374
Doom 3 Walkthrough - Doom 3 374

Lastly, jump off as the platform lowers to this doorway.

Doom 3 Walkthrough - Doom 3 375
Doom 3 Walkthrough - Doom 3 375

Battle an Imp and Trites before descending these stairs. Activate the panel to "Initiate Magnetic Field Discharge."

Doom 3 Walkthrough - Doom 3 376
Doom 3 Walkthrough - Doom 3 376

Return upstairs and jump across these platforms, timing your jumps to avoid the spinning cylinders, while simultaneously battling two Imps. Not easy. Heal at the health station far-left.

Doom 3 Walkthrough - Doom 3 377
Doom 3 Walkthrough - Doom 3 377

Open this storage area on the right for armor, shells and an ammo belt before continuing through the door on the left.

Doom 3 Walkthrough - Doom 3 378
Doom 3 Walkthrough - Doom 3 378

Ride another moving platform then toss a grenade or shoot the explosive barrels to send these Z-Sectors flying. Armor is behind the crates in the far-right corner.

Doom 3 Walkthrough - Doom 3 379
Doom 3 Walkthrough - Doom 3 379

More Z-Sectors are in the adjacent corridor, including this one who emerges from a secret panel behind you. Again, grenades are my weapon of choice. You'll find a clip and shells in the hidden area. You've now caught up to those who have extended the service bridge.

Doom 3 Walkthrough - Doom 3 380
Doom 3 Walkthrough - Doom 3 380

If you prefer a fighting challenge over jumping puzzles, extend the service bridge. Reload your chaingun first though, as these two shotgun-wielding Z-Sectors attack through the door behind you.

Doom 3 Walkthrough - Doom 3 381
Doom 3 Walkthrough - Doom 3 381

Follow the newly-extended service bridge to the other side.

Doom 3 Walkthrough - Doom 3 382
Doom 3 Walkthrough - Doom 3 382

Two Imps emerge from behind hidden panels on the left. Armor is in the right corner.

Doom 3 Walkthrough - Doom 3 383
Doom 3 Walkthrough - Doom 3 383

Extreme close up! Defeat the Imps and battle a series of Trites. Follow the service bridge to the unlocked door seen in the distance, battling a Z-Sector along the way.

Doom 3 Walkthrough - Doom 3 384
Doom 3 Walkthrough - Doom 3 384

A series of Trites crawls over this ledge. Save your game before continuing through the door to the left.

Doom 3 Walkthrough - Doom 3 385
Doom 3 Walkthrough - Doom 3 385

This is a tough room. Start with a grenade toss to this Z-Sector on the right. Retreat into the hallway immediately.

Doom 3 Walkthrough - Doom 3 386
Doom 3 Walkthrough - Doom 3 386

I found the chaingun to be the best bet on the remaining Z-Sectors, one to the left and one down the middle. Just remember to save some chaingun ammo -- you'll need it at the end of the level.

Doom 3 Walkthrough - Doom 3 387
Doom 3 Walkthrough - Doom 3 387

Enter and this maggot spawns behind you. Search the shelves for supplies, including the three medkits seen on the right.

Doom 3 Walkthrough - Doom 3 388
Doom 3 Walkthrough - Doom 3 388

A second maggot spawns once you walk behind these shelves. Continue through the door to the left. (This door is unlocked only for those who have activated the service bridge.)

Doom 3 Walkthrough - Doom 3 389
Doom 3 Walkthrough - Doom 3 389

Follow the service bridge where you'll find armor in the room ahead. This room is inaccessible to those who activated the EFR.

Doom 3 Walkthrough - Doom 3 390
Doom 3 Walkthrough - Doom 3 390

An Imp is waiting inside this hidden compartment. Defeat him then climb the ladder.

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Doom 3 Walkthrough - Doom 3 391

Battle Maggots, Trites and an Imp down this corridor to a ladder far-right.

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Doom 3 Walkthrough - Doom 3 392

Grab the armor on the right before following the service bridge to the door beyond.

Doom 3 Walkthrough - Doom 3 393
Doom 3 Walkthrough - Doom 3 393

Battle this Maggot and a Trite before healing at the station on the right.

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Doom 3 Walkthrough - Doom 3 394

Climb this ladder. Note the armor in the corner.

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Doom 3 Walkthrough - Doom 3 395

This Z-Sector attacks through the door. Storage locker 064 is accessible only to those who have extended the service bridge, and can be opened with code 651. Inside you'll find cells, armor and shells.

Doom 3 Walkthrough - Doom 3 396
Doom 3 Walkthrough - Doom 3 396

Through a series of doors then down these stairs you'll encounter a swarm of Trites. Your best bet is to hunker down in this corner and fire in short bursts. Armor and a medkit are under the stairs below.

Doom 3 Walkthrough - Doom 3 397
Doom 3 Walkthrough - Doom 3 397

Cross the service bridge and battle these well-entrenched Z-Sectors.

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Doom 3 Walkthrough - Doom 3 398

This is where the EFR and service bridge paths converge. Two medkits and an adrenaline hypo are found here.

Doom 3 Walkthrough - Doom 3 399
Doom 3 Walkthrough - Doom 3 399

Up some stairs and through a door you'll battle this Z-Sector. Remember to save some chaingun ammo.

Doom 3 Walkthrough - Doom 3 400
Doom 3 Walkthrough - Doom 3 400

Peer through this window up ahead to witness Campbell and Swann blowing up some Trites with the BFG.

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Doom 3 Walkthrough - Doom 3 401

Don't be caught off guard by this Imp lurking in an alcove to the right. Inside the alcove you'll find two clips.

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Doom 3 Walkthrough - Doom 3 402

Heal at this station and save your game before continuing through the opposite doors.

Doom 3 Walkthrough - Doom 3 403
Doom 3 Walkthrough - Doom 3 403

Yikes! A cutscene introduces your first boss - Vagary.

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Doom 3 Walkthrough - Doom 3 404

This is what you've been saving your chaingun ammo for. Unleash your chaingun on Vagary, dodging the objects she hurls at you with her telekinetic powers. Don't let her get this close.

Doom 3 Walkthrough - Doom 3 405
Doom 3 Walkthrough - Doom 3 405

Of course, if you have the plasma gun, it's time to let 'er rip! My preference still goes to the chaingun for this fight, but you'll want all the firepower you can muster against Vagary.

Doom 3 Walkthrough - Doom 3 406
Doom 3 Walkthrough - Doom 3 406

Once Vagary is defeated, open this now-unlocked door.

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Doom 3 Walkthrough - Doom 3 407

Activate the transfer bay panel to load the next level.

More Doom 3 Walkthroughs

This Doom 3 walkthrough is divided into 27 total pages.

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