The Secret Cellar
by Joan H. Young
Set in the 1950s, Cora Dubois, Jimmie Mosher and their friends, Laszlo, George, and Ruby, discover they have a talent for getting to the bottom of local mysteries.
In The Secret Cellar (Dubois Files book #1), Jimmie's family is in danger of losing their farm to the bank. Old Granny May seems to be trying to tell them something, but maybe she's just losing her mind.