Tintin, Captain Haddock and Professor Calculus head to Sydney to participate as special guests at an international conference on astronautics. While in the airport in Jakarta (Indonesia) waiting for your flight to Sydney, Pst meet Piotr, who had met at a previous adventure, collected on the album Stock coke. Pst pilot now working as eccentric millionaire Laszlo Carreidas. The latter invites the three protagonists to travel with him to Sydney in his private plane.
However, the Secretary of Carreidas, Spalding, and two of the crew of the aircraft are part of a plot to hijack the plane and divert it to a volcanic island in the Indian Ocean, site of a crash landing. Tintin, Haddock, Calculus and Pst are arrested; Snowy escapes but is shot by the hijackers and the others for dead.
Later it is discovered that behind the hijacking is the evil Rastapopoulos, which aims to gain the fortune Carreidas stored in a Swiss bank. Allan Thompson is the deputy Rastapopoulos. Tintin, Haddock and Calculus have fallen into their hands by a causality as Rastapopoulos unaware that travel with Carreidas. Taking advantage of the circumstance, however, Rastapopoulos plans to end their lives to avenge the defeats inflicted on him in previous adventures.
The protagonists are held in an old bunker Japanese World War II. Carreidas is taken to a bunker, where the evil Doctor ordered Rastapopoulos Krollspell (the name is possibly related to the Nazi physician Theodor Morell, Kroll can also refer to the opera house in Berlin that took place the meetings of the Nazi Reichstag) to inject to Carreidas a "truth serum" of his invention. The product is very successful, as Carreidas begins to confess all the evil he has committed since age four, but does not give the desired information Rastapopoulos. Incidentally, the doctor injects a dose of exasperation Rastaopoulos their serum.
Meanwhile, Tintin, Haddock, Calculus and Pst manage to escape the bunker where they had been locked, with the help of Snowy. They go to where is Carreidas. Rastapopoulos, because of the truth serum, Krollspell trusts that he intended to eliminate him as soon ceased to be useful.
Tintin and his friends burst into the bunker and then captured and Rastapopoulos Krollspell. However, Rastapopoulos escapes when you pass the effect of serum, Thompson meets and begins the persecution of Tintin and his friends. Guided by a strange voice in his mind, Tintin discovers, hidden in a strange sculpture depicting the head of an astronaut, a secret entrance leading into the volcano.
Inside the volcano, Tintin and his friends meet a strange character, Ezdanitoff Mik, who tells them that is in contact with an alien culture and that has attracted there by telepathy. Meanwhile, Rastapopoulos and his men find the entrance, but fail to open, so they use explosives. Ezdanitoff explains that the explosion will cause the eruption of the volcano, so you must go to the crater, where they can get help from aliens. Undertake the march there by underground passages, closely pursued by Rastapopoulos and his men. Litmus almost died due to toxic gases, but managed recatarle Tintin. After reaching the crater, Ezdanitoff mesmerize players, climbing aboard a flying saucer believing himself to be embarking on an airplane. Soon after, the aliens leave them in the ocean on a raft. Rastapopoulos and his men, however, are picked up by aliens, even under hypnosis, and will no longer be known about them.
When a plane takes Tintin and his friends, none of them (except for Snowy) remember what happened from the time they boarded the plane Carreidas. However, Professor Calculus retains a screw made of an unknown metal. In the last bullet, Tintin, Haddock and Calculus board the flight to Sydney, as planned.