Whale researcher Leon Anawak is concerned when an orca is found dead on the beach after allegedly attacking a fishing boat.

Whales are attacking tourists in Canada and lobsters are suddenly deadly in France. The Swedish scientist Dr. Johanson discovers aggressive ice worms on the seabed that are multiplying at breakneck speed.

Venice is experiencing an unprecedented plague of jellyfish. Charlie Wagner's best friend has disappeared with her research ship without a trace.

Cécile recommends stopping fishing off the coast and warning the population against using tap water. The ice worms are investigated more closely. Charlie returns to Shetland, where she reunites with her boyfriend Douglas.

When Rahim and Charlie report a light phenomenon and a sound that Jess has recorded, Johanson travels to Shetland. They receive a warning that a tsunami is heading for the Atlantic coast of Northern Europe and Shetland.

Johanson suspects that an unknown marine intelligence, which he calls Yrr, is behind all the results. He wants to contact the life form with a research mission and therefore asks the billionaire and entrepreneur Aito Mifune for help.

With humanity's future at stake, the team butt heads on what to do. In a desperate situation, Charlie makes a radical decision.