After the death of his son, Toby, the renowned scientist, Dr. Tenma (Nicolas Cage), creates a robot whom the calls Astro Boy (Freddie Highmore), hoping to replace his son. Astro boy is endowed with special powers, extra strength and powered by positive blue energy. Seeking acceptance and recognition, he comes into contact with many vivid characters during his journey. He understands the human nature and emotions. He also finds a very old robot, Zog (Samuel L. Jackson), and revives it. Finally, when his loved ones face danger, Astro boy returns to the city and saves them through his heroic deeds. Thus, he becomes a super hero and uses his powers against an alien invader too.