Sun.
Chris could feel the harsh burn of concrete against his shoulder as he skidded around the corner of an abandoned building. A rock smashed into the pavement in front of him, and from behind he could hear the fading jeers of the street gang that considered this particular area theirs. With a curse, he glanced at his watch - long since dead but worn out of habit - and put on the burst of speed. The sun would be setting soon and the temperature would drop sharply into freezing.
The temperature drop was the only way to tell when day stopped and night started. The sun hadn't been seen for over five years and the sky remained an unnatural red colour regardless of the passage of time.
Lance was waiting for him, one booted foot tapping idly against the wall. "You're late, you fucker. It's almost sundown."
Chris glanced around the alley and pulled his stained jacket closer; he could feel the temperature dropping already. "Yeah, I know. Had a run in with the Canaanites down on 4th."
With a snort Lance dropped down from his perch on the wall, one hand automatically sliding under his combat shirt to check the knives he carried at all times. They were all armed: you never knew when you'd have to defend yourself against some other fucker.
Lance went first, pulling a pile of rubbish off a manhole and yanking the cover to the side before dropping down. The clang of his boots on the ladder echoing off the cold concrete walls of the sewers. Chris followed, tugging the manhole cover back into place and yelping quietly when the metal froze to his fingers. Scrambling down the ladder, he caught up with Lance and they set off at a run, boots splashing through the ankle deep liquid until they reached the slightly drier crosspipe. Fifteen more minutes of running and they were scrambling up another ladder and back out into the freezing but somewhat fresher air of the uplands. In this case, another alley running alongside yet another a derelict building. They pushed through a pile of boxes and through a rusty metal door, and into the warm, dimly lit main room.
This was home, this was Eden.