During their investigation, Harry is captured by the Zygons, a shape-shifting alien race hiding in their submerged spacecraft. Their leader, Broton, tells Harry that their spaceship had sustained damage and landed on Earth centuries ago to await rescue, but when they discovered that their home planet had been destroyed in a stellar explosion they decided instead to conquer the Earth and terraform it to suit their physiology. To achieve this goal, they have captured several humans to use as "body prints" to infiltrate key leadership positions, including the influential Duke of Forgill who serves as head of the Scotland Energy Commission. They had also brought an embryonic sea creature called the Skarasen to Earth and augmented it with cyborg technology until it has reached giant proportions. They are directing it with a signalling device to attack the rigs as part of their larger plan.