When you reach Nimbasa City, you'll be able to find the Dropped Item, which is somebody's Xtransceiver. The moment you get this item, you will receive a call on it from the item's owner stating that they would like the Xtransceiver back. They will request to call you at numerous points, but the locations they call you are very specific, only 15 areas each on a specific tile. These are the exact tiles shown below. After a couple of calls, you will learn that the owner of the Xtransceiver is Yancy/Curtis, one of the presenters of a variety of TV programmes in Unova. Yancy will appear if you're male and Curtis if you're female.
See http://serebii.net/black2white2/droppeditem.shtml for more details.