Your arm darts out and grabs the water bottle, opening it up and taking a long drink. As your headache fades and your throat recovers, you reach out for the piece of paper. It appears to be a map, with red and green lines, blue dots, and a few, scattered purple squares. Before you can completely digest the information, you notice some sprawling writing in the lower left corner, and begin to read.
Welcome to the railroad. Right now, you're in a shack, safely hidden from the Reds. You're probably confused as to what, exactly, happened, so let me explain quickly.
The giant pile of rubble I pulled you out of was created a few days back, when this army appeared out of thin air. Soldiers, wearing full body armor and masks, wielding guns we'd never seen before. We call 'em Reds, because of the masks. People resisted, of course, but anyone who provided the tiniest bit of resistance was shot, and they would level city blocks just to kill a squad of rebels. This little group managed to survive and get out of the city, and build ourselves a little enclave, hidden from the Reds. For the past few days, we've been trying our hardest to help people escape them, but most who survived the initial invasion were executed or rounded up in camps. If you can get to the purple square on the map, we'll take you in, no matter who you are or who you were. Don't lose this map, even if it means you have to destroy it.
Oh, dear. Things do not look good for humanity. Well, you might as well try to figure out how to get to that purple square he was talking about.