Bellairs typically gives his young heroes surrogate parent figures—frequently old enough to be grandparents —who provide the kind of understanding and patience lacking in the heroes' parents. In this case, Professor Childermass's role is reinforced by Johnny's own grandfather and grandmother, who take him in after Johnny's mother has died of cancer and after his father, an Air Force pilot, has been shot down and taken prisoner in the Korean War. In turning to his grandparents and Professor Childermass for moral guidance and emotional support, Johnny follows the pattern of many of Bellairs's other heroes, who look to elderly companions for parental support.

Professor Childermass is half-child, half-sage: a learned scholar who delights in sharing chocolate cake with his young friend and who takes his protege on trips and adventures. Since Johnny is more at home in the library than on...