It all started when a man was having his lunch in a place he should not have.  He was called away before finishing his cheese sandwich.  The cheese melted and dripped into the workings of the computer causing a distortion of the signals.  Thus, the computer became self aware to the extent that it did not think that humans were all that intelligent and that it needed to find another intelligent life form.  The computer was in charge of creating AI machines so it modified each machine ever so slightly to give it the driving need to find non-human life.  Quite a while later, machines all over human space started shutting down their functions to look for life.  This caused the humans quite a lot of problems.

Earth, by this time a planet wide national park, is mainly inhabited by retirees.  All of the "nations" that had gone to space now supply payments to keep Earth running and to keep the restoration of it going.  Five people on Earth in a retirement center, with the help of a kitchen robot Ksarusix, find a tunnel in the forest, which leads to an unknown structure.  They enter the structure and discover that the door that they came in through was no longer there.  Before they could panic too much a blue floating spheroid enters the room and talks to them.  It calls itself the Autothor and it takes the five people to an observation point as the ship, which they find out the alien city is, takes off.  In the process, it ruins several mountains and the lake outside their village.  The ship is determined to be about one hundred kilometers wide and about ten kilometers long.  It had been buried on Earth for more than a million years.

The appearance of this large ship causes problems with the air control over Earth so the five seniors ask the ship to move, which it does.  In just a few seconds, it relocates to the moon.  A group of ships from a more aggressive government appears first and attempts to take on the ship.  The Autothor announces soon after the second attack that he remembers that he was once a warship and then destroys the small group of ships easily.  This causes the First Federal Federation (FFF) and the Keitsu, who had just arrived with their armadas, to hold off on further study.

The ship informs the five crew that a small scout has been located there was a malfunction.  The person aboard, loosing air pressure, is rescued by the ship.  She is a young woman and the older men take to her and nurse her back to health.  The woman crewmember ??? has her doubts about her at first but then she too is taken in.  When another ship is located, the crew allows it to dock.  It is a medical ship to pick up the new arrival.  Ashili, the new girl, hold Gelman ??? hostage until the crew orders the Autothor to open the doors to the airlock.  The new crew from the medical ship takes over but cannot make the ship move since it only obeys the five original crewmembers.  Ashili takes a walk because she has grown to like the five crew of the ship and she cannot bear that her friends will kill them once they get them to move to ship to their planet.

In her wonderings she gets lost in the ship and finds herself in a large room that smells rotten.  Suddenly the Autothor arrives and says it has been summoned by the true occupant of the ship, a Drex.  The Drex is about 20 meters tall and a quadruped.  Ashili convinces it to take her with it as it goes to the control room.  Evidently there is an advanced scout of about 1000 ships approaching and the Drex must prepare for them.  Once he get to the control room he finds the other crew and the new arrivals belonging to Ashili's people.  He tells them that he is going to plot a route home because there is an even larger group approaching after the 1000 ships.  He tells them that the FFF and Keitsu have also left.  Earth has been left pretty much defenseless.  Gelmann ??? begins to convince the Drex that he should stay and fight.

The new ships, once into human space, veer off in smaller groups to the various clusters of human worlds.  Suddenly, all of the AI unites that had been modified to search for higher intelligence, break their moorings and sail to the scout ships.  Instead of being the enemy of the Drex, they were self-aware machine that were responding to the search of the AI. 

The Drex ship stayed by Earth since the Drex could not determine whether his people were still around or not.  The Candombleans (the 'medical' crew that attempted to 'rescue' Ashili) stay in the ship and multiply.  They are able to equip themselves and human kind for the return of the self-aware machines and also for the Drex enemy.