Chapter 6-7

 The sign is a dead body from the plane crash. To me I think it symbolizes to them that they need to get real. Like the place that they are at is not a joke... It not a fun place. It is serious. An they need to start taking it as serious as it actually is. They need to buckle down and start listening. So  the "sign" symbolizes that right now is not a joke. It's real life.