The Dark Design
Philip José Farmer
 The shortest of the three plotlines is that of Richard Francis Burton and his friends. Reunited, Burton and crew once again begin traveling up river. At this point, many decades after resurrection, the stone supplies in the valley have begun to run out and technology has begun to break down. Also, for reasons unknown, the "little resurrections" have stopped, and people who are killed are not brought back to life. As they sail up river the crew encounters a group of ancient Egyptians who tell them a detailed story of the last attempt to reach the mouth of the river. This mission, which was launched by the Pharaoh Imhotep, included the giant whom Sam Clemens calls Joe Miller (believed by the Egyptians to be an incarnation of the god Thoth). This mission reached the end of the river, and found a massive waterfall. Scaling its sides, they eventually found a passage through to the polar sea. Descending a ledge which had been carved into the rock they found a cave filled with food and powered boats. While most of the Egyptians sailed to the tower, never to return, one died and took their story to the valley. Besides learning this story the group's main significant act is uncovering a pair of impostors within their midst. Under hypnosis, the neanderthal Kaz remembers when they last encountered an agent of the people who created the Riverworld. He noted at the time that every resurrectee had marking on their forehead which Kaz and other Neanderthals could see, but which were invisible to others. The exception was this agent. At the time Kaz noticed that Monat and Frigate also lacked these markings. However, before he could tell Burton, he was confronted by the pair, who hypnotized him into forgetting his discovery. Burton quickly concludes that Monat and Frigate are agents sent to spy on him. When he goes to confront the two, he finds that they have escaped. The second storyline deals with the real Peter Jairus Frigate. Unaware that an alien agent has been posing as him, this Frigate, whose life story is identical in most respects to the one which the phony Frigate told (the exception being the real Frigate was born and lived a few decades earlier than the impostor had claimed), has been living an ordinary life along the river. One day a ship docks near his home and he recognizes the two men who captain it as his childhood heroes Jack London and Tom Mix. Accompanied by the sufi Nur ed Din and the African warrior Umslopogas, the two men are traveling incognito up the river. Desperate to join his heroes, Frigate signs on the ship where he becomes a valued crew member, not revealing for years that he knows the men's identities. Eventually he admits that he knows who they are and the two men tell their story. They were each contacted by The Mysterious Stranger, who enlisted them to find the headwaters of the River. When the boat arrives at a metal-rich kingdom named New Bohemia, Frigate suggests that they speed their travel there by building a balloon. After a betrayal by the ruler of New Bohemia, the men eventually get their balloon and travel a good distance upriver, only to crash when they have a near-miss with another flying vehicle. The story of that flying vehicle is told in the third stream of the novel. This details the efforts of the nation of Parolando to build an airship. The ship, the brainchild of Parolando's president, the engineer Milton Firebrass, will be able to reach the pole more quickly than the two riverboats which Parolando has already constructed. Firebrass is assisted in these efforts by Cyrano de Bergerac, who has remained behind to work on the project. They are joined by newcomer Jill Gulbirra, an Australian dirigible pilot and strident feminist. Gulbirra, the most experienced lighter-than-air pilot in the region, quickly becomes important to the project, as does Cyrano, who, surprisingly, turns out to be the nation's best pilot. When the ship is built it sets off, under the command of Firebrass and Gulbirra, for the pole. Making its way through a massive hole in the mountains which surround the polar sea, the airship confronts the dark tower. Suddenly anxious, Firebrass, along with a few hand picked others, board a helicopter to descend to the tower. However, their helicopter is blown up shortly before landing, killing all aboard. The culprit is Barry Thorne, an engineer who had been working on the ship. While he is confined to a prison, the rest of the crew begins to explore the tower. They find an open door on the roof which leads into the structure. However, when they attempt to gain entry they become blocked by an invisible force. The only one who manages to enter the building is one of the pilots, a Japanese Sufi named Piscator, who never returns. After waiting some time for him to return, the ship reluctantly departs. After they return to the valley, they are cajoled by Clemens into conducting a revenge mission against King John. John had managed to persuade the pilot of a second Parolando dirigible to attack Clemens' ship, the Mark Twain. Seeking revenge, Clemens orders the larger airship, the Parseval, to conduct a mission to kidnap King John and return him for punishment. The mission, led by Cyrano, meets with some success, until John manages to escape as their helicopter attempts to return to the airship. Frustrated, the attackers return to discover that Thorne has escaped. He parachutes from the airship, which soon explodes from the bombs which he had planted aboard it.