The Terrans discover the existence of the Gravo-Tunnel, a transmitter like beam that connects the two planets Wassytoir and Baytuin. Rhodan and a small team are invited on Dacommion but they must go through the Gravo-Tunnel.

On an exploring mission on Wassytoir, Tschubai and Wyt discover a building where disformed Varbenians are kept. They have been victim of the Gravo-Tunnel, which sometimes malfunctions. Tschubai and Wyt try to warn Rhodan of the danger but they arrive to late: Rhodan has just entered the Gravo-Tunnel.

At the same time, a fleet of ten thousand Hulkoo spaceships enter the Nest system.