The World's Gerry Hadden reports from Spain on a massive immigration phenomenon. Every August, an estimated one-and-a-half million people leave Europe for North Africa. They are immigrants going back to their native countries for vacations. Right now, the immigrants are heading back to their jobs in Europe. This year, though, their return comes at a time of heightened security alerts in Europe. That means tighter controls and longer lines at the Spanish port of Algeciras.