Though a short novel, this story has layers of meaning that will repay many readings. Tim is a worrier. He is sure he will never come to anything. All he knows about are snails, and the only thing he can do well is draw straight lines, and how can he keep a family by doing those things? Tim's mother thinks he is 'the dearest boy in all the world', and it is only after he goes to beg on a street corner that we learn his father has died, and he has been told that he must be the man of the family now. Another 'layer' of the story has to do with Tim's sister, Evie, who suffers badly with asthma. It develops that their father did too, and neither child has fully understood that he died in a car accident - nothing to do with his asthma. Both children have also worried that their mother might die, and this is brought out and talked over. The major theme of the story is that worries that seem to be about one thing are often about something entirely different, and that things perfectly obvious to adults are not so to children. An important book for parents as well as children.