The pristine waters of Cocos Island are a magnet for divers from all over the world. Known as the Island of the Sharks, famed for its huge schools of scalloped hammerheads and spectacular coral reefs.

In December 2017 this underwater paradise was horror-struck when a female tiger shark fatally attacked a diver and severely wounded another. The locals have named this monster predator Lagertha.

Dr Craig O’Connell, Vicky Vasquez and underwater cinematographer Andy Casagrande are on a mission to track down Lagertha, find out what makes her so aggressive, and try to understand what happened that day. Using cutting edge technology, will they come face to face with a killer?