At the great Intitute of Science, where the robots are made on huge assembly lines, a giant robot COLOSSO suffers a short circuit before he is ready for his electronic brain is completed. In this brainless state, he will smash everything in his way in, and destroy everything in his path and what ever he encounters. He will obey the first human being that gives him an order. As chance would have it, the first man he encounters is a criminal that is an expert of safe-cracking banks. Soon Colosso becomes the pawn of the band of the theft game. Astro Boy comes to the rescue as the criminals are executing their most sensational theft. He apprehends the criminals and returns Colosso to the Insitute, where the huge robot is completed and becomes a ‘good guy’ after all the commotion.