Jason Carter is an actor at the tail end of a Civil War movie.  Some of his co-workers are having problems with the way the movie is being made and so cause a delay in the filming.  During this delay he finds a CD-ROM on the ground and puts it in his pocket.

An unknown entity called a Monitor muses about the fact that she can tell there is something wrong with the planet she is supposed to be watching.  She struggles with the idea that it could be in her mind but decides otherwise.

The movie shoot is finally finished and Jason returns his costume to wardrobe when the disk falls out of his pocket.  Marjorie, the lady in charge of wardrobe, puts it in her computer and is able to decrypt it and find the owner's location and that there is a $1000 reward if returned.  She convinces Jason to go with her to south Georgia to return it.

They head out to Peru and find a guide.  After several days of journeying they reach a rock wall and some caves.  There is nothing extraordinary about them so they plan to leave the next day.  That night they are confronted by Fewick and held at gun point so they would tell the world about the discovery.  They try to explain that they have no interest but to no avail.  Moe, Fewick's cat, chases Macha, a cat that Jason had found and brought along with them, into the forest.

Some archaeological treasures are found but before much more can be done da Ramini, a lady from the town Cuzco that Jason had talked to before, shows up with two men armed with AK-47's.  They tie Jason, Ashwood, Igor and Fewick up and start looking for treasure themselves.  They find hidden stores full of gold and the prisoners assume that they will be killed.  Suddenly a woman with a video shows up.  She is Tran Ho, a journalist that was asking Jason questions on the set of his last movie.  It becomes apparent that she is not out to rescue anyone, however, since she just wants a good story.

After a while of exploring the caves, da Ramini and her companions discover an egg-shaped item that they require Fewick to look into.  After he gets to the scene, his cat Moe shows up and decided to jump onto the egg.  The egg starts to glow and then a brilliant light envelops the group.  They soon discover that they have been teleported to Nazca, another ruin, about 200 miles away.

The group enters back into the cave there and place the cat back on the egg thinking that it will take them back to Paititi.  Instead they are transported to another world where they meet the descendants of the Incans. 

These people have advanced technologically with help from a race they call Those-Who-Came-Before.  These are the people that left the matter transmitters and they also left teaching machines.  The Incans decide that, since the matter transmitters are working again, they will return to Earth and take out their revenge on Spain who had conquered them.

After preparing their forces, the Incans load twelve cargo ships full of troops and send them along a different matter transporter.  The general and his entourage (along with the prisoners) take the smaller transmitter and follow.  When they get to Nazca, they find that the twelve troop transports have been filled with salt water and fish and there is no sign of their army.

That night Igor, Jason and Ashwood hear a cat in the transmitter room and the go to investigate.  It is Macha, the cat that Jason had found earlier.  They put her on the transmitter like they had Moe previously.  She starts the transmission and they find themselves back at Paititi.  Before the Incans can follow, Jason accidentally steps on Macha's tail and she jumps on the egg, clawing it.  The transmitter blows up keeping the Incans from following.

Outside Paititi, a spacecraft disguised as a palm tree, crashes and three vegetable shaped creatures emerge.  They tell Jason, Ashwood and Igor that they are Those-Who-Came-Before and that they are responding to the use of the gateway.  They agree to help them stop the Incans from taking over Europe and getting revenge on Spain because their gateway was not meant to be used for conquest.

The Incans fall back on a contingency plan that would have them use the teaching machines to help gain mind control of the European nations.  In order to do this they need to broadcast to at least 50% of the population.  They get help from Tran Ho, Fewick and the Fernandez brothers to do this by setting up a live broadcast of a science fiction soap opera using the gold they discovered in the ruins to fund it.

The new aliens neutralized the Contisuyans.  They decided that the only way the Contisuyans could attempt a take over without troops was to use the learning machine to take over peoples minds.  They set about trying to find out what they were up to.  They learned that they had been broadcasting in Europe and that they had been sending out signals to get people to hate Spain.  They also learn that England and Spain were to have a soccor tournament the day after a special presentation of the The Day Before Tomorrow, their show.  This would cause mass chaos sparking a global movement against the Spanish.

They find out from where they are broadcasting so determine that Those-Who-Came-Before (the Boojums) could modify the signal but that they would have to have a audible part with it.  Jason and Ashwood say that they will break into the studio long before anyone gets there and Jason would walk on at a specific time and start acting.  That would be the signal to the Boojums.  After some problems getting to the studio, everything eventually goes off as planned.  However, during the broadcast, Fewick's cat discovers what Jason is doing and attacks him to stop his plan from being destroyed.  Macha and the cat that came with the Boojums attack him because he revealed himself to them.  The cat is defeated and the studio burns down but none of the humans or Boojums are any the wiser about the true identity of their cats.

The Boojums shut down the gateway and leave Earth.  The Contisuyans are stranded there but they make due with their situation.  Much later, de Ramini and Fewick show up to offer Jason a part in a new movie.  They had become famous for their sci-fi soap opera and now had their own production company.  Just to show that there were no hard feelings, they were offering him a part and he accepted.

Ashwood had found her own pack and extracted a second flashlight.  Now she played the beam over the ruins of the ovoid.
    "This sucker's not gonna be sendin' nobody nowhere for a long time.  We're safe."
    "I stepped on Macha's tail," Carter told her.  "You saw what happened after that.  She jumped on top of the transmitter and started pawing around.  Crossed some circuits somehow... I don't know."  He helped Igor bind his undershirt around his forehead.  "You're okay?"
    She nodded.  "I was farther down that you guys when it blew.  Notice the silence?"
    With a start Carter realized that the explosion had been soundless.  It seemed to him that like the build of a certain actress he knew, such a thing defied various natural laws, but then so did the transmitter itself.
    They found Macha lying stunned and apparently otherwise intact at the base of the far wall, her fur smoking slightly.  The cat responded to Carter's presence with a couple of uncertain meows.  She offered no resistance when he picked her up.  Slowly she began to preen herself.