The scientist Professor Roch invents an explosive with immense power. He can use it to replace coal and oil, but it can also destroy the entire world. The pirate Artigas kidnaps Professor Roch and takes him to an island in the Atlantic Ocean, where a city is located inside an extinct volcano. Artigas provides Professor Roch with all the means to complete his invention and assures him that he will use it for humanitarian purposes. However, his assistant Hart soon discovers the truth. He tries to escape...