Prof. Laurent Akush from the Institute of Geophysics is working on a device that can be used to locate coal underground. For successful work he needs a tube XCX13, it is available in the West, but foreign firms sabotage the supply of the device. In his institute there is an enemy engaged in sabotage, but the professor does not believe in enemies. He believes that this is propaganda, science is above ideology, and that "scientists are made of a different dough." Laurent Akush receives an invitation to the international geological congress in Berlin, there he hopes to meet an old American friend, the scientist McLane. He takes with him his assistant Ferenc Ervish and a young Stakhanovite worker, Ishvan Kadosh. The professor does not yet know that in Berlin, Colonel Thompson of American intelligence is preparing a trap for him.