Ok, so, let's say that this ship recently sent a distress call. You, as a newly recruited special ops trooper, are sent with your squad to investigate. Your ship waits outside and serves as your base throughout the game. Each member of your team gets certain specialties, and you can add teleporter beacons that lead back to your ship at anytime, but you only get three. As you're exploring, a ship is towing you back to base. After exploring through corridors full of dead bodies, you come upon a group of aliens feasting on a dead crewmember. "Oh my god," says one of your teammates, and the aliens attack. After you kill them, you need to bring back a corpse to your ship so you can beam it back to base. then, you go exploring around untill you come upon some aliens attacking a locked door. once you kill the aliens, you find 4 injured troops inside. The troops will come under your command, and if you bring them back, then they tell you what happened, and you can move on. But, if they all die, you lose. The solider tells you that theres a hole in the outer airlock, and that's how they got in. As soon as you get back into the ship, the power goes out, limiting your visibility. You go to the power core and find aliens and the mini-boss ripping up the room. To kill the boss, you need to kill all the aliens in the room, then have one person use a certain special ability, then repeat twice. Command your solider to go up to the damaged core, and it will instantly repair. Your communication equipment suddenly cuts out, making it impossible to talk to anyone besides the people around you. You need to make it to the communications room to fix the relay, then to the bridge so you can use this larger ship to talk with the base. When you make it to the communication room, everything is dark (like, stacking in a defense map dark). You say to your squad, "Don't get disoriented by the dark. Try to keep your bearings, and whatever you do, DO NOT decide that this is a good time to go crazy and lose yourself." This is a hint for the players to group (ctrl + #) their troops. Once inside, you spot a switch. You guess that it turns on the power in this room, so you turn it on. "I have a bad feeling about this..." says one squadmate, and another says, "Yeah, it's unnaturally quiet... Kinda eyrie..." When you activate the power, doors open, unleashing all matter of aliens (cue scary sound effects and violin vibrato here). When the room is cleansed of aliens, you need to get to the bidge to use the ships powerful communication relay. But, when you get to the door, you find yourself in a cutscene.
YOU: Why won't this door open?!
SOLDIER YOU SAVED EARLIER: Hmm... Maybe the aliens busted the door controls, or maybe.....
YOU: What?
SQUADMATE: I don't like the tone of his voice...
SOLDIER: Maybe the computer locked it because of something on the other side... Gives me the chills just thinking about it...
SQUADMATE: Got that right!
YOU: Come on, troops! Now isn't the time to freak out. Is there any other way that we can get through this door?
SOLDIER: Well, there's the security center, that's where all the surveilance screens and door overrides are.
YOU: Ping it on our RADAR maps and we can get going. Let's move, people!
So then you have to go to the security center. Once you get there, you go and check the screens. And another cutscene:
YOU: Uh-oh...
SQUADMATE: I don't like uh-ohs when we are on a big creepy ship with aliens around...
SQUADMATE: What, what is it? *moves closer to you (by way of trigger)* Oh my god....
YOU: Towship, we have a problem...
*View centers on bridge, which is the end of land and goes into space*
YOU: The bridge is gone.
When you leave the room, you say, "Soldier, where is this outer airlock? I think we need to go have a check." So, it gets pinged, and you head off. You return to your ship for suits, then go off to a location pinged on the minimap. When you get there, you find creep on the ground and a hoarde of aliens blocking your way. You fight through the aliens in your new suits (make main people hero version) and you find the UBER BOSS! Figure out a way to kill this guy, and you win... or do you? When you kill the boss, you find that more aliens are swarming onto the ship, and there are some climbing the cables to the tow ship. After a dramatic cut-scene that goes something like:
YOU: Towship, they're climbing the cables to your ship. You need to abort and come back later.
TOWSHIP: No! I can make it back to base before they can make it to me! Just get those alien *insert random swear word here* offa me until we make it back!
YOU: It's too risky you'll--
TOWSHIP: That's an order!
you get the objective to kill the aliens on the cables. After you kill them all, more rush past you, and another cutscene:
YOU: There's too many!
TOWSHIP: No! We can make it! I'll send a call for reinforcements!
YOU: No! There's no time! Cut the cable!
TOWSHIP: I refuse to leave you there!
YOU: If you don't, I will!
TOWSHIP: Oh... Alright, but I will come back with help!
YOU: You better.....
Now, you need to destroy the cable moorings. After that, survive for two minutes, and reinforcements will come and pwnage the aliens. After that, there's a cutscene that ties up the loose ends in the story line, such as "What were those things?" and "Will there be a sequel to this?" After the cutscene, you win.
Ownage storyline to rock your socks.