The mystery of the Ghost Tree involves the old legend that a tree on the land that Gideon and Pascal wish to acquire is haunted.

The deeply superstitious and not very bright Gideon is frightened out of his wits at the prospect of owning a piece of land that has a haunted tree on it. But because he's none too intelligent and lacks confidence in front of white men, he simply goes along with what Pascal says when they're at the Freedman's Bureau looking for some land.

When the white man at the Freedman's Bureau asks Gideon and Pascal if they're superstitious about owning a plot of land with a ghost tree on it, Pascal says no, and Gideon, unable to think for himself, just goes along with Pascal. In actual fact, however, he's deeply superstitious and so certainly doesn't relish the prospect of a haunted tree being on his property.