Writer-director Joss Whedon, the creator of the TV series Buffy the Vampire Slayer, saves the world from destruction yet again in the first of the summer blockbusters, Marvel’s The Avengers. The adventure is moderately enjoyable but rather exhausting.

If you haven’t seen previous Marvel comic book movies—Iron Man and Iron Man 2, Thor and Captain America: The First Avenger—or if you’ve seen them but haven’t retained the plot threads, it may take you half an hour or so to get your bearings.