You arrive at Mars, but are immediately pursued by Martian authorities. You have no weapons. You must run. Start by going through that "Authorized Personnel" door on the left.
Through this door on the right, then the next door on the left.
Descend these stairs then take the door on the left.
Use the door on the right.
Run down these stairs.
Run all the way to the bottom of the stairs. You'll pass many hysterical women here -- very funny.
Continue through these doors, then through the second door on the left.
LOTS more screaming. Continue through the door far-right.
Run into the smoking room. Grab the medium medkit on the middle chair then exit out the doors on the right.
Go through the "Authorized Personnel" door and descend the stairs.
Exit out the Database Conversion Department door then continue through the door far-right.
Avoid the guard seen here as you charge out this door.
DON'T go up the stairs. Instead, go around the air duct to the right.
Exit out this door.
Drop below to end this level and load the next.
You drop onto a guard and take his pistol.
You can also pick up a Beretta R2 once you drop these guys.
This is an open area that can be traversed multiple ways. You'll want to ultimately proceed through that door ahead.
Several gunmen are waiting above.
Proceed to this difficult firefight. Do your best to take cover and isolate one enemy at a time.
Upstairs you'll find the large medkit seen by the door.
Jump as indicated onto a moving crate.
Hop over these horizontal beams so that you are not pushed off the crate.
Battle the guards up ahead and prepare to jump off where indicated.
Take out all the guards in this area.
You'll find medkits here.
Activate the console (1) then the console (2) to extend the bridge (3).
Cross the bridge and defeat the newly-spawned enemies. Activate this yellow panel on the right and a crane moves a barrel into place. Shoot the barrel as seen here to cause an explosion which will clear the way through those crates.
Note the medkit on the left; climb the stairs on the right.
Clear out the area of enemies then proceed through the door on the right.
Continue through here.
The large medkit on the right is always here.
Continue through this door labeled, "Processing".
Take out the guards in this room before passing through the door on the right.
Turn left and keep a safe distance from the barrels before shooting them, clearing out the corridor ahead.
Repeat on this corridor to the left.
I guess this guy was sick the day they taught the lesson about hiding behind explosive barrels.
Note the medkit here.
Continue through this door.
Take out the lone guard (visible on the stairs to the left) and grab the small medkit seen directly ahead.
Continue through these two doors.
Stay right then climb this ladder.
Take mild damage by walking through the vapor then turn this valve to stop the flow.
Climb the next ladder and fight your way to these leaking pipes.
Fight your way up these stairs to the right of the leaky pipes. (A medium medkit can be found further to the right of the stairs.)
Drop below and turn both valves.
Return to the leaky pipe area and find it clear to drop below.
Fight your way through this door.
Turn the valve on the left, allowing you to climb the ladder on the right.
You'll come to this room with lots of guards. Be especially careful of the guards on the catwalk above.
Climb this ladder on the opposite side of the room.
Continue along the catwalk ahead.
Drop to the floor below.
Approach the exit sign to initiate the ending cutscene.
In the cutscene, Mike Gomez fires a tranquilizer dart into Chaser.