Today you can watch the final act of online supervillain musical Dr. Horrible's Sing-Along Blog, before the entire tale disappears from the interwebz on Sunday at midnight. Though the first and second acts were sweet and goofy, show creator Joss Whedon managed to make this final installment genuinely upsetting. Dr. Horrible has been mostly a failed science supervillain up to this point, characterized by his unrequited crush on Penny and an inability to perfect his Freeze Ray. But in the latest installment, as you can see in this clip, he emerges as a true supervillain who has penetrated the inner circle of Bad Horse and his Evil League of Evil.

In this scene, Horrible has committed the first true crime of his career, beating Captain Hammer with his exploding Death Ray and accidentally killing Penny in the process. This isn't exactly where you might have expected this musical to go, since the tone was so light in the first two acts.

I was pleased to see the bad guy winning, especially because so-called good guy Captain Hammer was such a dick and Neil Patrick Harris has made Dr. Horrible a very sympathetic mad scientist. One of the best parts of the episode, which you should watch for yourself, is the incredible scene where Dr. Horrible beats Captain Hammer — he leaps out of hiding with his amazing Freeze Ray, interrupting a hilarious and insulting song that Hammer is singing to the homeless about how "everybody is a hero but mostly me."

It's rare to find a show that can reveal layers of character during a musical number that takes place in a satirical universe where heroes wear rubber gloves. And yet Whedon and Co. have pulled it off here. Now that Dr. Horrible has an origin story, complete with tragic death and a bunch of cool supervillain pals, the show ends just as it's really ready to begin.

Like most of the people who've flocked to this online experiment in fictional videoblogging, I am hoping to see more of Dr. Horrible. But please, don't make it a TV show. Just keep it real — keep it in blogland. We deserve a brilliant web show. Something that's as good as Homestar Runner and the Goddamn George Liquor Program, but totally different.

You can catch the whole thing online, buy it on iTunes for $4, or wait for the DVD.