Charlie Wagner, a young marine biologist, is assigned to a remote outpost in the Shetland Islands. During a survey, Charlie discovers large amounts of methane ice on the water surface, which is usually only found at great depths on the sea floor. And other strange incidents are happening in different regions of the world. While a fisherman in Peru dies unnoticed by a school of fish, in Canada, off Vancouver Island, the humpback and gray whales are a long time coming. When an orca is found dead on the beach after allegedly attacking a fishing boat, young whale researcher Leon Anawak is concerned. Eventually, the whales return in large numbers. Leon immediately drives his boat out to sea. His good friend Lizzie also starts a trip with her excursion boat full of tourists. But no one suspects what behavior the animals will show.

Whales are attacking tourists in Canada and lobsters are suddenly deadly in France. The Swedish scientist Dr. Johanson discovers aggressive iceworms on the seabed that are multiplying at breakneck speed. And with Charlie Wagner, a tragedy is brewing.

Venice is experiencing an unprecedented plague of jellyfish. The biologist Cécile Roche has an adventurous assumption about the deaths. Charlie Wagner's best friend has disappeared with her research ship without a trace. In Canada, researcher Anawak is getting to the bottom of whale attacks.

Cécile Roche reports to a commission on the dramatic situation on the French Atlantic coast.

Dr. Cécile Roche detects in crabs that have overrun coasts around the world the same bacterium that entered drinking water on the French coast via infected lobsters.

Charlie and Johanson have returned to Kiel. They attend a UN meeting in Geneva, where Dr. Roche predicts a worldwide threat to the drinking water supply.

"Thorvaldson" sets course for the Arctic, where a particularly large number of Yrr signals have been detected. Anawak and Crowe believe that it is possible to communicate with the Yrr there.

Aito Mifune is flown in by helicopter to personally learn about the research results on board the "Thorvaldson".