READ: The ritual of remembrance is different this year. Here's why.

A quarter-century after 9/11, the threat is coming from within.

I actually recall the sound of my shoes echoing off the floors of the U.S. Capitol. That musty marble has a sound (and smell) unlike any other. I was just a teenager from Indiana, selected to serve as a Congressional Page in the post-9/11 era. A messenger on Capitol Hill. Washington was a different place then. A heavy sense of duty hung in the air, and …