It's finished! Arthur the cat did what no one had managed before: he caught an unknown radio signal from space. But the discovery turned out to be a disaster. Arthur faces expulsion from Gradburg University if he fails to prove the existence of aliens within two weeks...Finally! The experiment is entering its final stage. Soon this small, backward planet will fall into a trap and take its place in the grandiose plans of the conquerors of the Galaxy... Will a stubborn student, his inventive friends and... Ulysses the Fox, who, of course, appear at the right moment, be able to save the Earth?