When a whistleblower exposes unnatural behaviour and mass deaths in wild salmon, marine biologist Johanne is dispatched to Norway’s deepest fjord. Her mission is to investigate possible negative effects of sonic lice treatment at a local salmon farm. But what starts as a routine assignment in familiar territory quickly develops into something far more serious when two young boys on a water scooter meet a brutal, inexplicable death, followed by more maimed bodies. It turns out that the sonic technology Johanne is investigating doesn't just affect salmon lice; it has also awakened the mythical Kraken, an ancient multi-armed monster ready to crush and devour anything that moves or dares to make a sound.