The Swarm

Charlie Wagner, a young marine biologist, is sent to a lonely outpost in the Shetland Islands. During a survey, Charlie discovers large amounts of methane ice on the water's surface, something that is usually only found at great depths of the seabed.

On the French Atlantic coast, the chef of a luxury restaurant dies in agony after liquid splashes on his face while he's preparing a lobster. Renowned molecular biologist Dr. Cécile Roche attempts to trace the cause of death.

While Venice suffers an unprecedented plague of jellyfish, molecular biologist 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, but political leaders are skeptical. Elsewhere, Sigur and Tina are back on board the Thorvaldson to survey the seabed for ice worms.

Dr. Roche detects the same bacterium in crabs that have invaded coasts all over the world. In Kiel, Professor Lehmann has bad news for Sigur.

Charlie and Sigur return to Kiel. At a UN meeting in Geneva, Dr. Roche predicts a global threat to drinking water supplies. Sigur gives a name to the unknown ocean intelligence he suspects is behind it all: Yrr.

The Thorvaldson heads for the Arctic, where many Yrr signals have been detected, and Leon and Crowe believe there is a way to communicate with the Yrr.

Mifune is flown in by helicopter to see the research results on board the Thorvaldson, and the scientists around Sigur want to find out as much as possible about the Yrr with further experiments.