Stop what you are doing. No, wait. Finish this, then go over to “Dr. Horrible’s Sing-Along Blog” and watch the first and second installments of Joss Whedon’s latest project. Hurry. Time is running out.

Whedon, the man behind the TV shows “Buffy the Vampire Slayer,” “Angel,” and “Firefly,” has produced one of the most unique Web shows to date and, in the process, is conducting his own experiment regarding online distribution.

Instead of producing another “LonelyGirl 15,” “Kate Modern,” or “Prom Queen,” Whedon and friends developed a three “act” “show” that plays this week only. It’s not a three-minute episode, available once a day, for a month or two.

ACT ONE became available for streaming on Tuesday, July 15.

ACT TWO will be available for streaming Thursday, July 17.

ACT THREE will go up Saturday, July 19.

Each act lasts about 15 minutes, with the whole “show” clocking in at just over 42 minutes. The show uses the Hulu video player and the quality is excellent.

All acts will be available until midnight, Sunday, July 20, after which they will “vanish into the night, like a phantom (but not THE phantom — that’s still playing, Like, everywhere,” Whedon said in his letter, “A Letter from Joss Whedon.”