A giant meteoroid approaches the earth, spotted from an observatory by Professor Decimus Phostle. A prophet, Philippulus, predicts the end of the world. The meteoroid misses the earth, but a fragment of it plunges into the Arctic Ocean. Phostle determines that the object is made of a new material which he names Phostlite, and sets off to find it with a crew of European scientists. Accompanied by Tintin and Snowy, their ship, the Aurora, is helmed by Tintin's friend Captain Haddock. Meanwhile, another team has set out aboard the polar expedition ship Peary, backed by the financier Mr. Bohlwinkel; wherefore, the expedition becomes a race to land on the meteorite. On the day of departure, Bohlwinkel has a henchman plant a stick of dynamite on the Aurora, but it is found and thrown overboard. In the North Sea, the Aurora is almost rammed by another of Bohlwinkel's ships, but Haddock steers out of the way. Further setbacks occur at the Icelandic port of Akureyri, when Haddock is informed that there is no fuel available. He and Tintin then come across an old friend of his, Captain Chester, who reveals that there is plenty of fuel and that the Golden Oil Company (which has a fuel monopoly) is owned by Bohlwinkel. The three then secretly run a hose from Chester's ship, Sirius, to the Aurora, and thus trick Golden Oil into providing the fuel they need.
Close to the Peary, the Aurora receives an indistinct distress call from another ship and alters its course to help, but inquiries by Tintin expose that the distress signal is a decoy to delay them. Resuming the journey, they intercept a cable announcing that the Peary expedition has reached the meteorite but not yet claimed it. While the Peary crew rows to the meteorite, Tintin uses Aurora's seaplane to parachute onto the meteorite and plant the expedition's flag. Tintin makes a camp while Aurora's engines are repaired after developing trouble. The next day he discovers that Phostlite accelerates growth, and makes things much larger: his apple core grows into a large tree while a maggot grows into a huge butterfly, and Tintin is menaced by a giant spider that escaped from his lunch box, and immense, explosive mushrooms before rescue arrived. A sudden seaquake shakes the meteorite to its core, and it sinks into the sea, just as Tintin and Snowy escape to the Aurora with a piece of Phostlite. After that Bohlwinkel learns that he is expected to be tried for his crimes.