Dr. Horrible is a low-rent super-villain whose main goal is to get into the Evil League of Evil. In his online video blog he talks about his arch-nemesis Captain Hammer and Penny, a girl from the laundromat that he admires from a distance.

After accidentally introducing Penny and Captain Hammer in the first place, Dr. Horrible is devastated that they seem pretty close. He concentrates on his freeze ray heist but after another setback, Bad Horse insists on a special demonstration of evil.