On their third day without food, Billy shows his sons how to draw the symbol. He takes a handful of charred kindling, burnt out in the pot-bellied stove, and gives a piece to each of them. He uses the bottom of a mug to make the outer circle, shows them how to hold it steady against the plasterboard wall and trace around its rim. He should have a compass but he sold his, borrowed the boss’s when he had to.