Tintin and his friends head out to Cuthbert Calculus' estate on a mysterious lake in Syldavia. They end up discovering a large criminal gang in a base on the bottom of the lake ruled by Tintin's old enemy Rastapopoulos, who goes under the name of 'King Shark'. Calculus has invented a machine which can reproduce objects in three dimensions, which Rastapopoulos tries to steal to use in an art forgery racket.