The sudden and unexpected arrival of a mysterious package interrupts Hat Tintersmoot's twelfth birthday. Where did it come from? Who left it? Once she discovers that the small cardboard box is a gift from her Grandpa Gordon, the mystery deepens...considering the fact that he passed away three years ago.

The handwritten note reads, "Inside this box is an impossible mystery that only the purest of hearts can ever hope to uncover. Solve it, and you will discover the answer to one of the greatest secrets ever."

It's another perfect job for the owner of The Marshmallow Hammer Detective Agency. With the help of a new best friend, and her first official employee, Hat must uncover the truth behind five nearly impossible clues in order to find the answer.

The Mysterious Case of the Golden Egg is a heartwarming tale full of riddles, puzzles, and thoughtful messages about life, love, and happiness.