The paperback editions of The Boxcar Children Mysteries: #9, Mountain Top Mystery; #10 Schoolhouse Mystery; #11, Caboose Mystery; and #12 Houseboat Mystery are offered together in a cardboard case.
The Boxcar Children Mysteries Boxed Set #9-12

The paperback editions of The Boxcar Children Mysteries: #9, Mountain Top Mystery; #10 Schoolhouse Mystery; #11, Caboose Mystery; and #12 Houseboat Mystery are offered together in a cardboard case.