Dr. Drabble, Genius Inventor Books in Order

While traveling with their missionary parents, PJ and Chelsea sneak away with Dr. Drabble's musical invention in Egypt. Their plan for revenge creates unexpected trouble, bringing the question of forgiveness into their adventurous journey.

PJ and Chelsea use Dr. Drabble's duplicating invention while visiting the Philippines, hoping it will provide an easy way to make friends. Their shortcut brings complications that force them to reconsider whether avoiding effort is worth it.

Traveling toward England with their missionary parents, PJ and Chelsea discover that Dr. Drabble's new dust can make objects fly. They use it to search for God, but a dangerous mishap changes their understanding of where divine presence can be found.

During a visit to Brazil, PJ and Chelsea mock people whose appearances differ from theirs. Dr. Drabble responds with an invention that changes their own size, turning their behavior into an uncomfortable lesson about prejudice.

Dr. Drabble's new mirror makes PJ and Chelsea invisible, allowing them to explore Japan unseen. The freedom soon brings problems, especially when the children must consider whether being unnoticed excuses taking things without paying.

PJ and Chelsea see Dr. Drabble's duplicating machine as a way to avoid chores. Breaking their promise not to use it alone creates unexpected complications, turning a tempting shortcut into a lesson about keeping their word.

Dr. Drabble's invention lets PJ and Chelsea breathe underwater while exploring seas near Australia. The adventure offers excitement, but forgetting their responsibilities creates danger and makes the children reconsider how they use their unusual opportunity.