Tom cuts what is traditionally called a "Faustian bargain", trading his soul to the Devil in exchange for worldly favors. In the context of the story this detail is left out, being referred to as something that "need not be mentioned" but is "generally understood" in such circumstances. This emphasizes that the focus of the story is not upon the exact course of the plot, because we already have a pretty good idea of what's going to happen; Tom is going to try to skip out on the bargain, and the Devil is probably going to collect his soul anyway.
Surely enough, as Tom ages he loses his carefree attitude and begins to think about death and the fate that awaits him, and attempts to alleviate his fears by going to church and carrying Bibles. The Devil catches him at the door one morning, his protective Bibles misplaced, and puts him astride a black horse, which gallops out of town and into the swamp, apparently to the old Indian fort where Tom first met the Devil, and thereafter Tom disappears. All of Tom's worldly possessions are either transformed into useless junk, or destroyed by natural acts. It is suggested that his ghost still haunts the swamp.