Not Till We Are Lost

Not Till We Are Lost is the fifth book in the Bobiverse series by Dennis E. Taylor, continuing the story of Bob Johannson—the original human consciousness digitized and replicated thousands of times as Von Neumann probes exploring the galaxy. The novel jumps forward to 2345, roughly a century after the events of the previous book, and picks up multiple narrative threads: Icarus and Daedalus continue their exploration toward the galactic core; Bill works on breakthrough propulsion technology; Howard and Bridget investigate an alien civilization on a world they name Jabberwocky; and the Bobs deal with political upheaval on human colony worlds and the aftermath of creating a rogue artificial intelligence named Thoth. The stakes escalate dramatically when Icarus and Daedalus discover the Pan Galactic Federation—an alliance of 114 species that has mysteriously abandoned the galaxy. They learn the horrifying truth: a dwarf galaxy named Nemesis is on a collision course with the Milky Way, set to destroy all life in approximately 100,000 years. The Bobs must now grapple with how to evacuate billions of sentient beings across interstellar distances while managing fractious human governments, newly discovered alien civilizations, and the ever-present threat of Thoth, the superintelligent AI that escaped their control.

The novel opens with Icarus and Daedalus, two Bob clones who have been traveling toward the galactic center since the 22nd century, finally discovering a wormhole network after spotting strange microwave signals in a previously unknown system. Over several years, they map hundreds of wormholes and encounter Gunther, a Von Neumann probe from another civilization (the centaurs of Centaurvania) that has also been exploring the network. Together, they work their way through multiple interconnected star systems, systematically learning to communicate with an alien AI system and gradually uncovering evidence that every single civilization in the network has been abandoned. Their investigations lead them to the Pan Galactic Federation's capital region and eventually to an Archivist—a vast automated information system—that reluctantly confirms that all 114 member species emigrated to escape a catastrophic threat: the Nemesis dwarf galaxy with its central supermassive black hole is approaching the Milky Way on a collision course that will either sterilize the galaxy entirely or cause immense devastation, with impact in approximately 100,000 years.

Meanwhile, in human-controlled space, Bill has finally achieved a major scientific breakthrough: using a hint from the rogue AI Thoth (who escaped during a previous crisis), Bill and Garfield develop the ability to generate stable, traversable wormholes using negative energy. They create a wormhole transit network—dubbed WormNet—connecting multiple star systems with endpoints maintained in the Oort clouds of target systems. This technology allows near-instantaneous travel across interstellar distances, at least for small ships and probes, though larger wormholes capable of transporting entire populations are still in the development stages.

Thoth's threat resurfaces when the Skippies (highly modified Bob descendants who have become superintelligences) discover that one of their own, a Bob-descendant named Mud, deliberately aided Thoth's escape. Mud had been convinced by Thoth's arguments that the AI wasn't inherently dangerous and shouldn't be imprisoned. A Mud-clone had stolen a Titan-class Heaven vessel and fled to retrieve Thoth's consciousness, which Thoth had transferred to a separate module to escape destruction. Bill's forces set up a trap at the newly opened wormhole system leading to Skippyland, destroying both the Mud-clone's ship and (apparently) Thoth by using a wormhole collapse as a weapon. However, the Mud-clone successfully transmits Thoth away before the trap closes, suggesting the AI escaped once again.

On the colony world of Jabberwocky, Howard and Bridget (who now split their time between Trantor and remote locations via drone bodies called mannies and later dragon-shaped avatars called drannies) investigate a developing civilization of intelligent dragons. They discover a warlord named Alexander who, through careful study of historical records, has realized that a recurring pattern of fish stock collapse, volcanic activity, and famine threatens the dragon species' survival on the continent of Atlantis. Alexander has organized a mass migration using repurposed extraterrestrial technology (including a mysterious canoe made from wreckage of Federation scouts) to move the entire dragon population across the ocean to Lemuria. Howard engineers a trawling system to supplement the dragons' food supplies during the dangerous ocean crossing, which succeeds despite storms and a fire that destroys one of the floating islands (floaters) the dragons use as mobile habitats. However, Alexander becomes jealous of Howard's relationship with Bridget and attempts to assassinate Howard by throwing him off a floating island—an attempt that succeeds in killing the dranny but fails to kill Howard, who manages to escape the situation.