Her underwear

"Wait," Isabel said as she panicked remembering she wasn't wearing any underwear. "Can't you just pat me down? My flight leaves soon."

"I suppose I can but only if the alarm doesn't go off again. If it stops going off then you're free to leave, if not we might have to take you to do a thorough investigation," the security guard explained.

Isabel nodded and held her arms up as she was patted down. She was then sent through again, but the alarm went off again, she frowned as she was patted down again, and the same thing happened.

The security guard pulled her to the side again this time taking a wand out and waving it up and down her body.

The alarm goes off.