Reduced to desperation by dishonest enemies, Robert Drayton attempts unsuccessfully to burglarize a house in Philadelphia. To his embarrassment, Drayton meets an old friend, Terence Trenmore, who by chance is staying in the house. Trenmore proves to be both understanding and compassionate, and soon he is showing Drayton an odd crystal vial filled with a strange dust reported to be from Purgatory. Trenmore accidentally inhales some of the dust and vanishes, followed soon by his lovely sister Viola and by a guilt-driven Drayton.
The three regain consciousness in a bizarre and shadowy realm named Ulithia, through which they make their way to a bright, moon-shaped gateway. They pass through the gateway only to find themselves in a transformed Philadelphia in the year 2118.
The three time travelers quickly find themselves in serious difficulties, as the civil liberties to which they are accustomed have been outlawed by a totalitarian government based on a twisted version of the history of the great Quaker statesman William Penn. At this point the focus of the novel changes, and character and drama move to the background in favor of social satire.
A series of confrontations with the Philadelphia au-thorities puts Drayton and the Trenmores, along with a blundering, time-traveling burglar they have met, on the verge of being put to death. Terence Trenmore heroically precipitates the destruction of the sacred temple which is the headquarters of the local government and plunges himself and his companions back to the place and time in which their adventures originated. Soon Drayton and Viola Trenmore become engaged to marry. The novel ends with the three making plans to repair Draytons fortunes in Cincinnati.
In the light of this conclusion and of the fact that the powerful dust has been stolen at the end of the novel, it seems likely that Francis Stevens intended to write a sequel to this work. That possibility is further supported by the enigmatic references within the text to Andrew Power, whose name recurs in several notable passages.