The main theme of Catch Us If You Can by Catherine MacPhail is the challenge of growing up and learning about the importance of responsibility. Without a father or a mother, Rory has to grow up fast and burden the responsibility of taking care of his ageing grandfather who is gradually becoming senile.
This is a big responsibility for Rory and he tries his best to perform his duty as a filial grandchild. The truth is, he performs his duty wholeheartedly. For instance, he saves his Granda from setting himself on fire and being a danger to himself and others. He also makes a decision to rescue his Granda from Rachnadar, a home for the aged, when he realises that the latter is not unhappy at all being there.
Unlike other boys his age, Rory has not time to play football because he gives it up to take care of his Granda. He also rushes home after school so that he can buy lunch for his Granda. In addition, he hides his Granda’s pipe in order to discourage the latter from smoking. Apart from this, Rory ensures that his Granda takes his medications on time and behaves properly in public.
During their adventure, Rory placed great importance on the welfare of his Granda, and every decision was responsibly made. For a boy his age, this is outstanding, as most boys his age would not have been able to cope with the problems.