The past.
A mysterious being named Calibso arrives in the Archi-Tritrans system. He meets Skopein, a barbarian, whom he trains in order to make a "guardian". He says he has already recruited seventeen guardians throughout the galaxy, among which seven are active. He takes Skopein in the main station of the transmitter, PP-III. Callibso leaves the frightened barbarian on the station to pursue his mysterious quest. Unfortunately for Skopein, the station is trapped : the Lemurs have left behind some kind of spore. Initially destined to be used against the Halutians, the spores turned out to be ineffective against their armor-like skins. Skopein unknowingly touches the spores which quickly take over his body and kill him.

The present.
Perry Rhodan wants to install a solar transmitter within the Sol system in order to have an emergency exit if the Larens managed to break through the Anti-temporal Tidal Field. To achieve this, another expedition led by Atlan is sent to Archi-Tritrans. Its mission is to examine the transmitter and see if Goblin, the small neutron star orbiting one of the two suns forming the transmitter, could be moved into the Sol system.

Meanwhile, the Larens are not staying idle. They have designed the Timescout, a device that allows them to scan the close future in an attempt to locate the Sol system. Their fleet, led by Leticron, is keeping the location under close scrutiny. Atlan's ship, the Cagliostro, breaks through the blockade and escapes in linear space, heading for the center of the Milky Way.

Shortly after they have arrived near Archi-Tritrans, the two lost Explorers come out of the transmitter. A commando sent on Ex-1819 shows that the crewmembers are now living in symbiosis with some sort of plant and react with hostility to the Terrans, who leave the Explorer. The two Explorer spaceships suddenly set in motion. Before the Terrans can react, they are headed towards one of the two suns and disappear there.

Ras Tschubai teleports on PP-III and finds out about the fungus. Before he can react, some of the spores settle on his spacesuit. He is helpless to get rid of them and starts suspecting that they are a very dangerous organism. As the Terrans are giving up about taking control of the station, Alaska Saedelaere decides to use for the first time his "annihilation spacesuit". He puts it on and boards PP-III. The experiment is a success : the spores die at the contact of his spacesuit.

The control station is now accessible to the Terrans.