This cache is located in our front yard. It is an easy mystery to solve. The log book is located in the house of the Gnomes, which has a lock on their treasure chest.
To get the code for the lock, just solve the easy puzzle.
In the Gnome home along with the chest there is a laminated card with scenes from four different movies. Use the first letter from the name of each of the movie's and use those for the lock.