A missing letter is the key to the whereabouts of Fort Freedom, the stockade that disappeared after the Revolutionary War. The fort is located somewhere within the boundaries of Shoreham and has been sought after for many years, not only for its historic value, but for the gold supposed to be hidden there by the early settlers. The Pine Lake Parkway construction job brings this unusual disappearance to public notice and, of course, wherever there is a mystery the Happy Hollisters are sure to be in the thick of it.And "thick" is just the right word, for it is hoped that the fort will be uncovered by the great bulldozers and steam shovels that are building the new Parkway. With dust and dirt flying and houses being torn down the Hollister children search the area for some clue that will lead them to the missing letter, the site of Fort Freedom, or both. Here is a fast-moving Hollister mystery that offers exciting adventure with narrow escapes from the dangers of the construction area and the false trail laid for the children by a man whose identity remains as much of a secret as the location of Fort Freedom.