You should be standing by some stairs. Go left. Aliens are leaving the room. Run up to the door. It will open. Put out your gun, but don't shoot. The guy will stick up his arms. Then go right. He will then close the door permanently. Go right and then go up the stairs. Crouch in front of the wall. Put up a shield and then blow up the wall with a large laser blast. The guy will start to roll grenades. As soon as he starts, run left. Stand behind him and let him keep grenading for a minute or so. Then kill him. After his bones fall apart, teleport down (you're standing on a teleporter). Then put up a bunch of shields and kill the guy shooting at you. Then go to the right, over to the tube and press down. Shoot the power line and then go up.
Work you way back to the stairs and go down them. Notice the hole in the ground (grenades anyone?). Go down the hole and proceed to the right. The next screen will go dark. Just keep running. Guys will shoot at you from under a grate. After you pass the grate, stop. Walk SLOWLY to the right. When the screen changes, the lights will be back on. Jump over the hole and pull on the lever. Then go down the hole and run to the right. Just keep going right until you get to the wall. Then press up and you will teleport up. Then walk to the left. You will go thru a door and then your friend will fall. Follow him to the right. After he teleports, press up and you will teleport. Then follow him to the right and into the spaceship.
You're in the spaceship. The upper right corner of the screen shows the ship's control panel. Only two buttons show. Press them both. Then press the button to the lower left. A new panel of buttons to the left should turn on. Then press the top four buttons on that panel. A flashing button will appear. Press that button and you will eject.
Your pod lands poolside among a swarm of female aliens. Get out and run right. On the next screen over you will have to kill four aliens. (Shield, shield, big laser, little laser). After killing them, run right. On the next screen, your friend will bust throught the wall. Follow him right. A laser will then shoot out the ground from under you. As you fall, another alien catches you. He then kicks you into the next room. Your friend will come and jump on the other alien, and when he does, press right to squirm across the floor to a panel of levers. The alien will throw your friend off the ledge and then come after you.
When he's in the center of the screen, press your fire button and your will pull the first lever, killing the alien. Quickly, pull the second lever and a door will open from above. Press left to make your way to under the hole. When you get there, you will teleport up. That's the end. Just watch and enjoy.