The Happy Hollister children are off on another exciting mystery This time it all starts with a letter written in a funny code from Grandmother Hollister, who lives in Canada. The letter said: Dear Children, Gram is writing to you in code. It is braille. How would you like to visit me and meet a special friend? Also, I wish you could solve the mystery of the midnight trolls. With love, Gram The children begged to go visit...