Post-apocalyptic. Landscape is overrun with forests; thick, chocking forests. What left of us all fit on a train. We live on this train. We must keep it moving or else perish. No one knows what lives out there in those woods. We rarely stop; we cannot afford to stop. When we do stop it is for quick repairs: stumbling across another car to add to the train; locating food or fuel; fixing a wheel or a tie or the brakes. Each stop requires all hands.
There is unrest on the train though. Not quite disorder or revolt but serious grumbling. Rumors of a purge. It doesn’t make sense. We hunker down in one of the cars, myself and a friend and his pregnant wife. We hide there. We wait for this whole thing to blow over. While we hide on this car, we root around for supplies, trying to dig in. There is no way to know how long we will be here. This particular train car is self-powered; right now it’s being dragged along by the main engine but if we needed to, we could move ourselves. It has a diesel generator for power. And a nuclear reactor. After a while though, it seems to have gotten too quiet. We rush out of the car just in time to see the rest of the train pulling off into the distance, abandoning us.
From out of the woods comes a peculiar sound. There is a bridge not far off and we can make it there if only we can figure out how to engage the throttle.