Detective and mystery stories 11 Hardy Boys (Fictitious characters) 7 Drew, Nancy (Fictitious character) 6 Friendship 2 Mystery and detective stories 2 Animals 1 Boarding school students 1 Boarding schools 1 Bombs 1 Buried treasure 1 Conduct of life 1 Dueling 1 Fencing 1 Health resorts 1 Hogwarts School of Witchcraft and Wizardry (Imaginary organization) 1 Magic 1 Martial arts schools 1 Military aspects 1 Mystery 1 Oil industries 1 Orienteering 1 Parapsychology 1 Poaching 1 Resorts 1 Sabotage 1 Teacher-student relationships 1 Wizards 1 Youth 1