Capital Mysteries #11: The Secret at Jefferson's Mansion

"Goodbye, D.C.! Hello, Monticello!
"While painting a closet in the White House, KC discovers an old box full of handmade toy horses that once belonged to Thomas Jefferson. KC and Marshall go to Monticello, Jefferson’s home, to return the horses, but just after they get there, the box with the horses inside disappears! They have to explore historic Monticello, with its dank wine cellar, tiny dumbwaiter elevator, and spooky family cemetery to track down the thief before the horses are gone for good! "From the Trade Paperback edition."