Dr. Horrible, an aspiring supervillain with his own video blog, is attempting to join the prestigious Evil League of Evil (led by the legendary "thoroughbred of sin", Bad Horse), but his plans are usually foiled by the egotistical superhero Captain Hammer. Horrible's life is thrown for a loop when he falls in love with Penny, a beautiful and optimistic advocate for the homeless he meets at the laundromat, a situation which complicates itself even further when Penny begins dating the boorish, oafish Hammer after he apparently saves her life. Faced with the task of impressing the League, can Horrible overcome his own incompetence to ruin the day, kill the hero, and still get the girl?