The center of attention is the hapless supervillain Dr. Horrible, who often finds himself in various troubles. This is often thanks to the superhero Captain Hammer, who does everything to neutralize his enemy. In addition, the main character is deeply and unrequitedly in love with a young girl named Penny, who works at a laundromat. This secret passion adds to Dr. Horrible's problems. The supervillain has to balance between his work and courting the beauty Penny.