Dr. Horrible's Sing-Along Blog
The audience is introduced to the protagonist of Dr. Horrible and his quest to win over his dream girl Penny and to be accepted into the Evil League of Evil. Dr. Horrible is in the middle of stealing wonderflonium to create his time-stopping freeze ray when Penny asks him to sign a petition. Conflicted, Dr. Horrible decides that "A Man's Gotta Do, What a Man's Gotta Do" and go after the wonderflonium until he is interrupted by his nemesis, Captain Hammer. Captain Hammer ends up meeting and seducing Penny in the midst of thwarting Dr. Horrible.
As Dr. Horrible starts to befriend Penny through the social medium of laundromats, he discovers Penny has really fallen for Captain Hammer. Captain Hammer makes it apparent to Dr. Horrible that he's only using her to spite Dr. Horrible. Dr. Horrible decides to kill Captain Hammer as a way to get accepted in the Evil League of Evil.
Dr. Horrible crashes a banquet held in honor of Captain Hammer with his Death Ray in hand. He takes aim at Captain Horrible before it malfunctions. Captain Hammer takes ahold of the death ray and shoots it at Dr. Horrible, it instead explodes causing shrapnel to fly everywhere and pierce and kill Penny. Ironically, this was the death that Horrible needed to get into the Evil League of Evil.