In one of his walks, Tintin and Snowy are on a plane that seems to have problems. Approaching are attacked and the plane on the run. After recover learns that the plane has crashed in England.
Tintin goes to England in search of her attackers and ends on the trail of Dr. Müller, who captures him, but Tintin escapes and begins his persecution. During it, Tintin is in turn pursued by Thompson and Thomson who believe guilty of a robbery in a train.
Finally, according to Müller, Tintin comes to town where Scottish Kitloch sailed to a nearby island where they believe there is a monster (in clear reference to the Loch Ness monster). The island is not only the backbone of a gang of counterfeiters using a gorilla to scare away the curious with its amplified roars.