Scientist Charlie Wagner discovers a phenomenon at an outpost in the Shetland Islands that fascinates professor Lehmann; abnormal behavior of whales off the coast of Vancouver Island worries cetologist Leon Anawak.

As whales attack tourists in Canada and lobsters are turned deadly in France, a scientist discovers aggressive worms multiplying at speed.

While Venice suffers an unprecedented plague of jellyfish, Dr. Roche discovers that a mutated bacterium is the cause of a growing number of deaths on the coasts; on Vancouver Island, Leon also suspects a mutation.

Dr. Roche informs a commission about the dramatic situation on the French Atlantic coast; Sigur and Tina return to the Thorvaldson to survey the seabed again for ice worms and find the worms have continued to spread.

Dr. Roche detects the same bacterium in crabs that have invaded coasts all over the world; Professor Lehmann has bad news for Sigur; Tina persuades Sigur to go with her to Geneva to check whether ice worms have also been found in other seas.

Charlie and Sigur return to Kiel; at a UN meeting in Geneva, Dr. Roche predicts a global threat to drinking water supplies.