It's a long, drowsy summer at the end of the 1980s, and Alan Dean and three of his friends cross the fields behind their village to look for a rumoured WW2 air raid shelter. Only half believing that it even exists beyond schoolboy gossip, the four boys nevertheless feel an odd tension and unease. And when they do find the shelter, and go down inside it, the strange and horrifying events that follow will test their adolescent friendships to breaking...