It's called, The Secret of Grandmother's Grandfather Clock.
This book will soon join the first two installments of the series, The Cat Burglars and Funny MoneyMystery, which have not yet been published.
The Story
Kurt loved to visit his grandparents’ farm. But, not this
time. A simple phone call changed everything. His grandfather had been a bomber
pilot and, together, they’d built models. When the phone rang, Kurt was nearly
finished building the first one that could actually fly.
His
grandparents lived a long distance away. When the family finally got there, Kurt
and his sister Olivia found out that their grandfather had died. But the
biggest shock was that someone may have been responsible for it.
So, Kurt,
Olivia, and their cousins set out to discover the truth. What they find is
someone had been threatening the old man and now they were trying to scare Kurt’s
grandmother.
His
grandfather had left some clues, but they didn’t make sense to Kurt until he
noticed a mirror. He also found out someone in the county office had been
tampering with property records and several people had already lost their
farms…but why?
https://www.youtube.com/watch?v=UHjJX7IYlqw