Box in the Mail

I received a box in the mail today. Books. My books. My books that I must sell. "Yippee," and "Oh, crap," collided in time and space like two electrons going around the CERN Superconducting Laboratory and trying to occupy the same slice of bologna that some careless worker left behind. It got me thinking though, as most things do in my overly-charged brain, about having a character in my story receive a mysterious package.

How would your protagonist react to a mysterious package ending up on his/her desk? Open it like a Christmas gift or call Homeland Security to blow it up?

P.S. I also can't believe this is the last day of the summer months.